Blowback is a system of operation for self-loading firearms that obtains energy from the motion of the cartridge case as it is pushed to the rear by expanding gas created by the ignition of the propellant charge .
207-449: The Thompson submachine gun (also known as the " Tommy gun ", " Chicago typewriter ", or " trench broom ") is a blowback-operated , selective-fire submachine gun , invented and developed by Brigadier General John T. Thompson , a United States Army officer, in 1918. It was designed to break the stalemate of trench warfare of World War I , although early models did not arrive in time for actual combat. The Thompson saw early use by
414-421: A United States Army Materiel Command engineering course from 1970, "The advanced primer ignition gun is superior to the simple blowback because of its higher firing rate and lower recoil momentum. However, favorable performance depends on timing that must be precise. A slight delay in primer function, and the gun reverts to a simple blowback without the benefit of a massive bolt and stiffer driving spring to soften
621-410: A gas-operated , long-stroke piston rod actuated by propellant gases bled through a vent in the barrel. The bolt is locked by a rising bolt lock. The weapon fires from an open bolt . The spring-powered cartridge casing extractor is contained in the bolt and a fixed ejector is installed in the trigger group. The BAR is striker-fired (the bolt carrier serves as the striker) and uses a trigger mechanism with
828-659: A "cup" to support the stock of the rifle when held at the hip. In theory, this allowed the soldier to lay suppressive fire while walking forward, keeping the enemy's head down, a practice known as " marching fire ". The idea would resurface in the submachine gun and ultimately the assault rifle . It is not known if any of the belt-cup devices actually saw combat use. The BAR only saw minor action in France during World War I, being brought into action only as late as September 1918, less than three months before Armistice Day . The intentional delay had been inspired by General Pershing ,
1035-515: A "submachine gun". Thompson intended for the weapon to provide a high volume of automatic, man-portable fire for use in trench warfare—a role for which the Browning Automatic Rifle (BAR) had been determined ill-suited. The concept had already been developed by German troops using their own Bergmann MP 18 (the world's first submachine gun) in concert with their Sturmtruppen tactics. The first Thompson entered production as
1242-419: A 1980s design by A.F. Barishev . The Mamontov and Goryainov rifles are only partially automatic; only the bolt unlocking is powered by the gases pushing the cartridge back, while the rest of the cycle (ejection, reloading) is done manually as in a traditional bolt-action rifle. A major problem with using the case cartridge as piston is that its motion is much faster (about 1 ms) compared to tapping gas further down
1449-411: A 500-pound (230 kg) bolt to keep the cartridge safely in the barrel during the first few milliseconds. Yet the bolt must cycle far enough back to eject the spent casing and load a new round, which would limit the return spring to an average force of 60 pounds-force (270 N). The resulting system, if it could be built, would not have enough energy to cycle reliably or even keep the bolt closed when
1656-505: A 9mm, .308 Winchester based cartridge with a .22 Hornet blank cartridge in place of the primer. Upon firing, the Hornet case sets back a short distance, unlocking the action. The case cartridge itself has been used experimentally to actuate the action similar to Garand's primer-actuation. Known prototypes using this method of operation include two 1936 rifle designs, one by Mihail Mamontov and another by Makar Goryainov at TsKB-14 , and
1863-407: A barrel chamber with pressure relief ports that allow gas to leak into an annular chamber during extraction. Basically the opposite of a fluted chamber lubrication as it is intended for the cartridge to stick to the chamber wall making a slight delay of extraction. This requires a welded-on sleeve with an internal annular groove to contain the pressure. John Pedersen 's patented system incorporates
2070-418: A breech block independent of the slide or bolt carrier. When in battery, the breech block rests slightly forward of the locking shoulder located in the frame of the firearm. When the cartridge is fired, the cartridge case, bolt and slide move together a short distance until the breech block strikes the locking shoulder and stops. The slide continues rearward with the momentum it acquired in the initial phase while
2277-403: A cartridge malfunction ("jam"). Reloading an empty drum with cartridges was a difficult and involved process in which the 50 rounds would be inserted and then the magazine wound up until a minimum of 9 to 11 loud "clicks" were heard before seating the magazine into the weapon. In contrast, the "XX" twenty-round box magazine was light and compact. It tended not to rattle, and could be inserted with
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#17327724938492484-421: A chamber ring near the shoulder which is used to avoid bolt-bounce rather than a delay element. Similar operations exist using a fluted chamber for delay. When the round is fired, the cartridge sticks to the fluted chamber walls making a slight delay of extraction. The prototype 6x45mm SAW caliber Brunswick light machine gun is an example that used this operation. Another example using a ported chamber that uses
2691-409: A chamber-ring delayed firearm, the chamber is conventional in every respect except for a concave ring within the chamber wall. When the cartridge is fired, the case expands into this recessed ring and pushes the bolt face rearward. As the case moves to the rear this ring constricts the expanded portion of the case. The energy required to squeeze the walls of the cartridge case slows the rearward travel of
2898-567: A closed bolt. The Cook automatic rifle was 30 inches retaining the barrel length of 18 inches. The last US-made variant was produced in 7.62×51mm NATO , as T34 Automatic rifle . The BAR also found a ready market overseas and in various forms was widely exported. In 1919 the Colt company developed and produced a commercial variant called the Automatic Machine Rifle Model 1919 (company designation: Model U ), which has
3105-511: A combined daily output of 706 rifles and a total of approximately 52,000 BARs were delivered by all sources by the end of the war. Between 1918 and 1919, 102,174 BARs had been manufactured jointly by Colt, Winchester, and Marlin-Rockwell. By July 1918, the BAR had begun to arrive in France, and the first unit to receive them was the US Army's 79th Infantry Division , which took them into action for
3312-477: A common solution is to grease the ammunition to reduce the friction. The case needs to have a rebated rim because the front end of the bolt will enter the chamber, and the extractor claw hooked over the rim therefore has to fit also within the diameter of the chamber. The case generally has very little neck, because this remains unsupported during the firing cycle and is generally deformed; a strongly necked case would be likely to split. The API blowback design permits
3519-576: A contemporary semi-automatic variant of the M1918 called "1918A3-SLR", and a much modified lightened version called HCAR (Heavy Counter Assault Rifle), which are legal for civilians without an FFL (federal firearms license) to own. Although the Colt Monitor version of the BAR failed to interest US civilian buyers in the midst of the Depression, the underworld was a lot more interested: in 1936
3726-743: A contract for the weapon and it was hastily adopted into service (the water-cooled machine gun underwent further testing). Additional tests were conducted for US Army Ordnance officials at Springfield Armory in May 1917, and both weapons were unanimously recommended for immediate adoption. In order to avoid confusion with the belt-fed M1917 machine gun, the BAR came to be known as the M1918 or Rifle, Caliber .30, Automatic, Browning, M1918 according to official nomenclature. On 16 July 1917, 12,000 BARs were ordered from Colt's Patent Firearms Manufacturing Company , which had secured an exclusive concession to manufacture
3933-549: A contract to make rifles for the Belgian government, acquired the Mayo Radiator Co.'s factory and used it exclusively to carry out production of the BAR. The first unit from this source was delivered on 11 June 1918 and the company's peak output reached 200 automatic rifles per day. Colt had produced only 9,000 BARs by the time of the armistice due to the heavy demands of previous orders. These three companies produced
4140-531: A different return mechanism compared to the M1918 (it is installed in the stock rather than the gas tube) and lacks a flash hider. Later the Model 1924 rifle was offered for a short period of time, featuring a pistol grip and a redesigned hand guard. These Colt automatic rifles were available in a number of calibers, including .30-06 Springfield (7.62×63mm), 7.65×53mm Belgian Mauser , 7×57mm Mauser , 6.5×55mm , 7.92×57mm Mauser and .303 British (7.7×56mmR) . All of
4347-579: A famous trick shooter of the early 1920s, purchased one of the first Colt-produced BARs to perform aerial target shooting exhibitions. Occasional BAR sales were made to civilian owners through distributors such as the Ott-Heiskell Hardware Co. In 1931, the new Colt Monitor was made available to civilians during the Depression at $ 300 each, including a spare parts kit, sling, cleaning accessories and six magazines, but Colt records indicate no domestic sales to individuals. After passage of
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#17327724938494554-580: A feature of a wide range of designs that can be traced back to Becker's, including the Oerlikon cannon widely used as anti-aircraft weapons during World War II. To increase performance of API blowback firearms, larger calibre APIB guns such as the Becker and Oerlikon use extended chambers, longer than is necessary to contain the round, and ammunition for APIB firearms come with straight-sided cartridges with rebated rims (rims that are smaller in diameter than
4761-596: A federal road in Sergipe was disrupted by armed Cangaçeiros in December 1937 who violently opposed any attempts to build roads near their territory. In 1938, the Thompson submachine gun was adopted by the U.S. military and was used during World War II . There were two military types of Thompson submachine gun: Over 1.5 million military Thompson submachine guns were produced during World War II. Military users of
4968-403: A fire selector lever that enables operating in either semi-automatic or fully automatic firing modes. The selector lever is located on the left side of the receiver and is simultaneously the manual safety (selector lever in the " S " position – weapon is s afe, " F " – f ire, " A " – a utomatic fire). The "safe" setting blocks the trigger. The weapon's barrel is screwed into the receiver and
5175-406: A gas piston. These omissions are conducive to relatively light construction by significantly reducing the number of parts required and the amount of machining required to produce a rifle. As the bolt head is driven rearward, rollers on the sides of the bolt are driven inward against a tapered bolt carrier extension. This forces the bolt carrier rearward at a much greater velocity and delays movement of
5382-453: A greater movement along the axis of bolt movement, essentially magnifying the resistance of the bolt without increasing its mass. The French MAS-38 submachine gun of 1938 utilizes a bolt whose path of recoil is at an angle to the barrel. The Jatimatic and KRISS Vector use modified versions of this concept. CMMG introduced the MkG carbine incorporating a radial-delay in 2017. This system uses
5589-538: A large bolt to handle the pressure of the round as well as a spring buffer shock absorbing butt plate on the stock to handle recoil. There were also a few rifles that chambered cartridges specifically designed for blowback operation. Examples include the Winchester Model 1905 , 1907 and 1910 . The only known assault rifle to use simple blowback was the Burton Model 1917. Although simple blowback
5796-450: A like-it-or-not basis led by Ott-Helmuth von Lossnitzer , the director of Mauser Werke's Weapons Research Institute and Weapons Development Group. Experiments showed roller-delayed blowback firearms exhibited bolt-bounce as the bolt opened at an extreme velocity of approximately 20 m/s (66 ft/s) during automatic fire. To counter bolt-bounce the perfect angle choice on the nose of the bolt head had to be found to significantly reduce
6003-462: A mechanical disadvantage, delaying the opening of the breech. When the cartridge pushes against the bolt face, the lever moves the bolt carrier rearward at an accelerated rate relative to the light bolt. Leverage can be applied with a dedicated part or through inclined surfaces interacting with each other. This leverage significantly increases resistance and slows the movement of the lightweight bolt. The reliable functioning of lever-delayed blowback arms
6210-420: A mere ounce of mass to the bolt. The Savage system employed the theory that the rifling in the barrel caused a rotational force that would hold the gun locked until the projectile left the barrel. It was later discovered that the bullet had left the barrel long before any locking could occur. Savage pistols were in fact operating as simple blow back firearms. The French MAB PA-15 and PA-8 9mm pistols feature
6417-469: A negative evaluation of Barishev's gun, pointing out that the main problems with reliability of firearms using the cartridge case as a piston were known since the 1930s and still unsolved. The Blish Lock is a breech locking mechanism designed by John Bell Blish based upon his observation that under extreme pressures, certain dissimilar metals will resist movement with a force greater than normal friction laws would predict. In modern engineering terminology, it
Thompson submachine gun - Misplaced Pages Continue
6624-424: A portion of the blowback to operate only certain parts of the cycle or simply use the blowback energy to enhance the operational energy from another system of automatic operation. What is common to all blowback systems is that the cartridge case must move under the direct action of the powder pressure, therefore any gun in which the bolt is not rigidly locked, and permitted to move while there remains gas pressure in
6831-450: A public demonstration of both weapons at a location in southern Washington, D.C. known as Congress Heights . There, on 27 February 1917, in front of a crowd of 300 people (including high-ranking military officials, congressmen , senators , foreign dignitaries and the press), the Army staged a live-fire demonstration which so impressed the gathered crowd, that Browning was immediately awarded
7038-462: A radial direction relative to the center of their bolt. The bearings engage corresponding pockets of the barrel extension when the bolt carrier group is in battery. The bearings are pushed outward due to spring pressure (e.g., a buffer spring) that compresses the carrier into the rear of the bolt. The carrier causes an internal component of the bolt carrier group named the lifter to push the bearings outward. The Lifter has angled grooves that interact with
7245-409: A rather heavy trigger pull and a stock with an excessive drop, increases the tendency for the barrel to climb off target in automatic fire. In 1927, the U.S. Navy ordered 500 Thompsons but requested a lower rate of fire. Thompson requested that Payne develop a method of reducing the cyclic rate of fire. Payne then replaced the actuator with a heavier one, and replaced the recoil spring with a stiffer one;
7452-440: A rear leaf sight with 100 to 1,500 yard (91-1,372 m) range graduations. As a heavy automatic rifle designed for support fire, the M1918 was not fitted with a bayonet mount and no bayonet was ever issued, though one experimental bayonet fitting was made by Winchester. During its lengthy service life, the BAR underwent continuous development, receiving many improvements and modifications. The first major attempt at improving
7659-629: A replacement for the M1918. The weapon also had a hinged shoulder plate and was adapted for use on a tripod mount. In 1932 Belgium adopted a new version of the FN Mle 1930 allocated the service designation FN Mle D (D— demontable or "removable"), which had a quick-change barrel, shoulder rest and a simplified take-down method for easier cleaning and maintenance. The Mle D was produced even after World War II in versions adapted for .30-06 Springfield (for Belgian service) and 7.92×57mm Mauser ammunition (for Egyptian service). The final variant in Belgian service
7866-519: A result the US Army was without a portable light machine gun until the introduction of the M60 machine gun in 1957. The US entered World War I with an inadequate, small, and obsolete assortment of domestic and foreign machine gun designs, due primarily to bureaucratic indecision and the lack of an established military doctrine for their employment. When the United States declaration of war on Germany
8073-596: A separate pistol grip and butt stock attached to a lightweight receiver, along with a shortened, 458 mm (18.0 in), barrel fitted with a 4-inch (100 mm) Cutts compensator. Weighing 16 lb 3 oz (7.34 kg) empty, the Monitor had a rate of fire of approximately 500 rpm. Around 125 were produced; 90 were purchased by the FBI . Eleven went to the US Treasury Department in 1934, while
8280-675: A similar design and work correctly. An unusual operation that uses a bolt head that moves rearwards when firing that allows the cartridge to move backwards or even stretching it until the bolt unlocks. When firing the cartridge moves the bolt head rearwards around 2.5mm until it stops, then rotates the bolt to unlock and cycle the operation. An operation using a "simple blowback" type bolt that has neodymium magnets to delay its operation. A special buffer using this operation has been developed by TACCOM. Other autoloading systems are: M1918 Browning Automatic Rifle approx. 11 kg (24 lb) (M1922) The Browning automatic rifle ( BAR )
8487-402: A simplified form of gas operation , since the cartridge case behaves like a piston driven by the powder gases. Other operating principles for self-loading firearms include delayed blowback , blow forward , gas operation , and recoil operation . In firearms, a blowback system is generally defined as an operating system in which energy to operate the firearm's various mechanisms, and automate
Thompson submachine gun - Misplaced Pages Continue
8694-422: A spade-type grip to the rear of the receiver, moving the main drive spring under the barrel and, most importantly, changing the feed system. Sustained fire was practically impossible with the standard 20-round box magazine, so a new feed mechanism was developed that was added to the receiver as a module. It contains a spring-loaded, bolt-actuated lever that would feed a round from a 91-round pan magazine located above
8901-572: A toggle-lock delayed-blowback-operated rifle. Also in 1884, a few months after Maxim, a British patent for blowback-operated pistols and rifles was filed by Richard Paulson. In 1887 a patent was filed by an American inventor called Carl J. Bjerkness for a blowback-operated rifle. In 1888 a delayed-blowback machine gun known as the Skoda was invented by Grand Duke Karl Salvator and Colonel von Dormus of Austria. The blowback (sometimes referred to as "simple", "straight" or "pure" blowback) system represents
9108-753: Is a family of American automatic rifles and machine guns used by the United States and numerous other countries during the 20th century. The primary variant of the BAR series was the M1918 , chambered for the .30-06 Springfield rifle cartridge and designed by John Browning in 1917 for the American Expeditionary Forces in Europe as a replacement for the French-made Chauchat and M1909 Benét–Mercié machine guns that US forces had previously been issued. The BAR
9315-558: Is called static friction, or stiction . His locking mechanism was used in the Thompson submachine gun , Autorifle and Autocarbine designs. This dubious principle was later eliminated as redundant in the M1 and M1A1 versions of the submachine guns at the insistence of the US Army. Lubrication or fouling would completely defeat any delay. Whatever actual advantage a clean, unlubricated Blish system could impart could also be attained by adding
9522-539: Is limited by specific ammunition and arm parameters like bullet weight, propellant charge, barrel length and amount of wear. John Pedersen patented one of the first known designs for a lever-delay system. The mechanism was also used by Hungarian arms designer Pál Király in the 1910s and 1930s and used in the Danuvia 39M and 43M submachine guns for the Hungarian Army . After World War II , Király settled in
9729-439: Is limited to guns using low-power rounds, it is so efficient that in small-calibre semi-automatic pistols it has become almost ubiquitous. Heavier calibre semiautomatic handguns typically employ a short recoil system , of which by far the most common type are Browning -derived designs which rely on a locking barrel and slide assembly instead of blowback. But blowback guns can be used to fire powerful cartridges if they are of
9936-406: Is not quickly detachable. The M1918 feeds using double-column 20-round box magazines , although 40-round magazines were also used in an anti-aircraft role; these were withdrawn from use in 1927. The M1918 has a cylindrical flash suppressor fitted to the muzzle end. The original BAR was equipped with a fixed wooden buttstock and closed-type adjustable iron sights , consisting of a forward post and
10143-483: Is purely academic. The important point is that it partakes some of the properties of both classes and, depending on the particular problem at hand, may be considered to be either one." In 1663 a mention is made in the journal of the Royal Society for that year of an engineer who came to Prince Rupert with an automatic weapon, though how it worked is unknown. In 1854 a hydropneumatically delayed-blowback cannon
10350-461: Is stripped from the magazine and chambered as the bolt returns to its in-battery position. The blowback system is practical for firearms using relatively low-power cartridges with lighter weight bullets. Higher power cartridges require heavier bolts to keep the breech from opening prematurely; at some point, the bolt becomes too heavy to be practical. For an extreme example, a 20 mm cannon using simple blowback and lubricated cartridges would need
10557-497: Is sufficient for the bullet to leave the muzzle and for the internal pressure in the barrel to decrease to a safe level. The bolt and cartridge are then pushed to the rear by the residual gas pressure. Because of high pressures, rifle-caliber delayed blowback firearms, such as the FAMAS , AA-52 and G3 , typically have fluted chambers to ease extraction. Below are various forms of delayed-blowback actions: Roller-delayed blowback
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#173277249384910764-468: Is the first weapon to be labelled and marketed as a "submachine gun". The original selective-fire Thompson variants are no longer produced, although numerous semi-automatic civilian versions are still being produced by the manufacturer Auto-Ordnance . These models retain a similar appearance to the original models, but have various modifications in order to comply with US firearm laws . Brigadier General John T. Thompson , who spent most of his career in
10971-721: The FN Mle 1930 was developed in 7.65×53mm Belgian Mauser by FN Herstal and adopted by the Belgian army . The Mle 1930 is basically a licensed copy of the Colt Automatic Machine Rifle, Model 1925 (R 75). The Mle 1930 has a different gas valve and a mechanical rate-reducing fire control mechanism designed by Dieudonné Saive , located in the trigger guard-pistol grip housing. Some of these FN rate reducer mechanisms and pistol grip housings were later purchased by Springfield Armory for evaluation and possible adoption on
11178-629: The .22 Long Rifle cartridge. Popular examples include the Marlin Model 60 and the Ruger 10/22 . Most blowback carbines and submachine guns are chambered for pistol cartridges such as the 9×19mm Parabellum, .40 S&W and .45 ACP. Examples include the MP 40 , Sten and UZI . The bolt can be made bigger and more massive in these weapons than in handguns, as they are intrinsically heavier and designed, ideally at least, to be fired with both hands, often with
11385-536: The Browning BAR . The SLA converted a .30-06 Browning BAR hunting rifle and a .243 Remington Model 742 to automatic fire by filing down the sear, and it was these weapons that were used in the shootout. At its inception, the M1918 was intended to be used as a shoulder-fired rifle capable of both semi-automatic and fully automatic fire. First issued in September 1918 to the American Expeditionary Forces , it
11592-663: The Cuban Revolution , the Thompson submachine gun was used by both Batista 's army and Fidel Castro 's guerrillas. Both the latter and the Brigade 2506 also used some during the Bay of Pigs Invasion . During the Vietnam War , some South Vietnamese army units and defense militia were armed with Thompson submachine guns, and a few of these weapons were used by reconnaissance units, advisors, and other American troops. It
11799-594: The Democratic Army of Greece were also using Thompson submachine guns, either captured from government forces or inherited from ELAS . ELAS was the strongest of the resistance forces during the period of Greek Resistance against the Germans and Italians and were supplied with arms from both the British and the United States. After the demobilization of ELAS, an unspecified number of arms were not surrendered to
12006-902: The Dominican Republic and developed the Cristóbal Carbine (or Király-Cristóbal Carbine) employing a similar mechanism. Other weapons to use this system are the Hogue Avenger and Benelli B76 pistols, the FNAB-43 submachine gun, the TKB-517 , VAHAN and FAMAS assault rifles, the Sterling 7.62 and AVB-7.62 battle rifles/light machine guns , and the AA-52 general-purpose machine gun. Gas-delayed blowback should not be confused with gas-operation . In gas-delayed guns
12213-540: The Grossfuss Sturmgewehr (with slightly more efficiency), and after the war by the Heckler & Koch P7 , Walther CCP , Steyr GB and M-77B pistols. When a cartridge is fired, the case expands to seal the sides of the chamber. This seal prevents high-pressure gas from escaping into the action of the gun. Because a conventional chamber is slightly oversized, an unfired cartridge will enter freely. In
12420-681: The Korean War M1918A2 production was resumed, this time contracted to the Royal McBee Typewriter Co. , which produced an additional 61,000 M1918A2s. A bullpup prototype existed as the Cook automatic rifle during the 1950s. It was developed at Benicia Armoury by US Army ordnance officer Lauren C. Cook. It used the gas operation of the M1918 BAR with the trigger group in front of the magazine. The operation fired from
12627-468: The M1903 Springfield rifle. This operation is one of the most simple forms of delayed blowback but unless the ammunition is lubricated or uses a fluted chamber, the recoil can be volatile especially when using full length rifle rounds. Rotation of the bolt should be at least 90° to prevent ruptured cartridges. Another form of this operation using a helical screw to delay rearward movement was
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#173277249384912834-468: The MGD PM-9 uses this operation. In toggle-delayed blowback firearms, the rearward motion of the breechblock must overcome significant mechanical leverage. The bolt is hinged in the middle, stationary at the rear end and nearly straight at rest. As the breech moves back under blowback power, the hinge joint moves upward. The leverage disadvantage keeps the breech from opening until the bullet has left
13041-710: The National Firearms Act of 1934, civilian BAR ownership was restricted even further. Importation of machine guns for transfer between civilians was prohibited in 1968 and the production of machine guns for civilian transfer was banned in 1986 . However, machine guns produced prior to 1986 are still transferable, and fully-automatic BAR models exist and occasionally come up for sale to qualified buyers. Some companies continue to manufacture semi-automatic copies for sale to civilians, such as Ohio Ordnance Works, Inc. , in Chardon, Ohio. Ohio Ordnance Works produces
13248-750: The Owen and Austen . Thompsons were also given to the Royal Australian Air Force and Royal Australian Navy . In Burma and India, British forces largely replaced the Thompson with the Sten gun . New Zealand commando forces in the South Pacific campaign initially used Thompsons but switched them for the more reliable, lighter, and more accurate Owen during the Solomon Islands and Guadalcanal campaigns. The U.S. Marines also used
13455-539: The SSG36 . On the other hand, because the design imposes a very close relationship between bolt mass, chamber length, spring strength, ammunition power and rate of fire, in APIB guns high rate of fire and high muzzle velocity tend to be mutually exclusive. API blowback guns also have to fire from an open bolt, which is not conducive to accuracy and also prevents synchronized fire through an aircraft propeller arc. According to
13662-539: The Salvator-Dormus M1893 machine gun and later the prototype Kalashnikov Model 1942 submachine gun in 1942 and the Fox Wasp carbine . David Marshall Williams (a noted designer for the U.S. Ordnance Office and later Winchester ) developed a mechanism to allow firearms designed for full-sized cartridges to fire .22 caliber rimfire ammunition reliably. His system used a small "piston" that incorporates
13869-922: The United States Marine Corps during the Banana Wars , the United States Postal Inspection Service , the Irish Republican Army , the Republic of China , and the FBI following the Kansas City Massacre . The weapon was also sold to the general public. Because it was so widely used by criminals, the Thompson became notorious during the Prohibition era as the signature weapon of various organized crime syndicates in
14076-467: The bolt is never locked, and so is pushed rearward by the expanding propellant gases, as in other blowback-based designs. However, propellant gases are vented from the barrel into a cylinder with a piston that delays the opening of the bolt. It was used by some World War II German designs for the 7.92×33mm Kurz cartridge, including the Volkssturmgewehr rifle (with little effectiveness) and
14283-414: The headspace and hence the correct positioning of the cartridges in the (closed) chamber. Due to usage wear the bolt gap between the locking piece and bolt head carrier is expected to gradually increase. It can be determined and checked by a feeler gauge measurement and can be altered by changing the cylindrical rollers for rollers with a different diameter. Installing larger diameter rollers will increase
14490-424: The muzzle , this functional seal is broken, allowing the propellant gas to be suddenly released in an explosive muzzle blast . The expanding gas also creates a jet propulsion effect rearward in the barrel against the spent cartridge case. This "blowback" is the predominant component of the recoil . Some guns use energy from blowback to perform the automatic bolt cycling /reloading process, while others will use
14697-399: The rotation of the bolt head to accelerate the bolt carrier of an AR-15 pattern rifle. The bolt locking lugs are adapted to incorporate 120° angles that rotate the bolt as it travels rearward under conventional blowback power. As the bolt rotates 22.5˚, it must accelerate the bolt carrier to the rear through an adapted 50° angle cam-pin slot. This acceleration amplifies the effective mass of
14904-416: The "L" 50-round drum and "XX" 20-round box magazines were tested 6 December 1941, at Fort Knox, Kentucky . An extended thirty-round box magazine and a forty-round magazine, which were made by welding two 20-round magazines face to face, jungle style, were tested. The testers considered both superior to either the "XX" box or "L" drum. The 30-round box was approved as the new standard in December 1941 to replace
15111-752: The "XX" and "L" magazines. (The concept of welding two box magazines face-to-face was also carried over to the M42 submachine gun.) The staff of Savage Arms looked for ways to simplify the M1928A1, and produced a prototype in February 1942, which was tested at Aberdeen Proving Ground in March 1942. Army Ordnance approved adoption (as the M1) in April 1942. M1s were made by Savage Arms and by Auto-Ordnance . M1s were issued with
15318-461: The "square" organisation of the time. When converting to the "triangular" organisation the separate BAR squad was eliminated with BARs going to each rifle squad. When the threat of a new war arose, Ordnance belatedly realized that it had no portable, squad light machine gun, and attempted to convert the M1918 BAR to that role with the adoption of the M1918A2 by the US Army on 30 June 1938. The BAR
15525-630: The .22 Rimfire cartridge. Williams designed a training version of the Browning machine gun and the Colt Service Ace .22 long rifle version of the M1911 using his system. The increased recoil produced by the floating chamber made these training guns behave more like their full-power counterparts while still using inexpensive low-power ammunition. The floating chamber is both a blowback and gas operated mechanism. Primer actuated firearms use
15732-551: The .45 ACP cartridge. The Thompson was first used in combat in 13 June 1921, when West Virginia state troopers fired on the mountainside near Lick Creek, where striking miners were firing at passing cars. By the time of the Battle of Blair Mountain , 37 had been acquired by the West Virginia state police and 56 were in the hands of coal companies and local law enforcement. The guns were also shipped to various hardware stores in
15939-652: The 1960s. They shipped their remaining stocks to arm the forces of Lon Nol 's Khmer Republic in 1975. They were then captured and used by the Khmer Rouge . During the Troubles (1969–1998), the Thompson was again used by the Irish Republican paramilitaries. According to historian Peter Hart , "The Thompson remained a key part of both the Official IRA and Provisional IRA arsenals until well into
16146-711: The 1970s when it was superseded by the Armalite and the AK-47 ." The Thompson was also used by U.S. and overseas law enforcement and police forces, most prominently by the FBI . The FBI used Thompsons until they were declared obsolete and ordered destroyed in the early 1970s. Because of their quality and craftsmanship, as well as their gangster-era and WWII connections, Thompsons are sought as collector's items. There were fewer than 40 pre-production prototypes. The Colt Patent Fire Arms Manufacturing Company in Hartford, Connecticut
16353-533: The 30-round box magazine and would accept the earlier 20-round box, but would not accept the drum magazine. The Thompson was used in World War II in the hands of Allied troops as a weapon for scouts, non-commissioned officers ( corporal , sergeant , and higher), and patrol leaders, as well as commissioned officers, tank crewmen, and soldiers performing raids on German positions. In the European theater,
16560-440: The 6.5×55mm-caliber Colt automatic rifles appear to have been sold directly to FN. An improved version of the Model 1924, the Model 1925 (R75), achieved the highest popularity in export sales. It is based on the Model 1924 but uses a heavy, finned barrel, a lightweight bipod and is equipped with dust covers in the magazine well and ejection port (some of these features were patented: US patents #1548709 and #1533968). The Model 1925
16767-725: The AEF commander, in order not to let the BAR fall into enemy hands too early. Fifty-two thousand BARs were available by the end of the war in November. During the interwar years, as the U.S. Army was reduced significantly in size, the BAR remained in the smaller extant Regular Army and by the 1930s, was also issued to state national guard units to be maintained at their armories . Given the part-time nature, smaller manning and lesser security of these national guard armories when compared to regular army installations, some BARs were subject to plunder by domestic civilian criminal elements. The BAR
16974-439: The BAR as a light machine gun, often fired from a bipod (introduced on models after 1938). A variant of the original M1918 BAR, the Colt Monitor machine rifle , remains the lightest production automatic firearm chambered for the .30-06 Springfield cartridge, though the limited capacity of its standard 20-round magazine tended to hamper its utility in that role. Although the weapon did see action in late 1918 during World War I ,
17181-505: The BAR did not become standard issue in the US Army until 1938, when it was issued to squads as a portable light machine gun. The BAR saw extensive service in both World War II and the Korean War and saw limited service in the Vietnam War . The US Army began phasing out the BAR in the 1950s, when it was intended to be replaced by a squad automatic weapon (SAW) variant of the M14 , and as
17388-598: The BAR series of firearms in Europe from Colt. The first BAR model sold by FN was the Kg m/21 (Kg— Kulsprutegevär or "machinegun rifle") chambered for the 6.5×55mm m/94 cartridge. The m/21 is a variant of the Model 1919 designed to Swedish specifications and manufactured initially by Colt's and later under license at the Carl Gustafs Stads Gevärsfaktori in Eskilstuna. Compared to the Model 1919,
17595-571: The BAR under Browning's patents (Browning's U.S. patent 1,293,022 was owned by Colt). However Colt was already producing at peak capacity (contracted to manufacture the Vickers machine gun for the British Army ) and requested a delay in production while they expanded their manufacturing output with a new facility in Meriden, Connecticut . Due to the urgent need for the weapon, the request
17802-556: The BAR's sights were redesigned to accommodate the heavy-bullet 172-grain M1 .30-06 ball ammunition then coming into service for machinegun use. In 1931, the Colt Arms Co. introduced the Monitor Automatic Machine Rifle (R 80), intended primarily for use by prison guards and law-enforcement agencies. Intended for use as a shoulder-fired automatic rifle, the Monitor omitted the bipod, instead featuring
18009-454: The BAR. Composed of a mixture of Bakelite and Resinox, and impregnated with shredded fabric, the stocks were sandblasted to reduce glare. The Firestone Rubber and Latex Products Co. produced the plastic butt stock for the US Army, which was formally adopted on March 21, 1942. The M1922 machine rifle was declared obsolete in 1940, but they were used by Merrill's Marauders in Burma later in
18216-623: The BAR. Troops from the First Battalion of the Sixth Marines had talked the "doggies" of the US Army's 36th Division into trading their BARs for their Chauchats. However, complaints from officers of the 36th resulted in the issuance of a command from Marine Lt. Col. Harry Lee on 9 October 1918: All Browning guns and equipment in Marine possession were to be turned in. The M1918 is a selective-fire , air-cooled automatic rifle using
18423-553: The Browning patents to produce the BAR that had been withheld from issue during the war. This allowed Colt to make the BAR available for commercial sale, including to civilian owners. The Colt Automatic Machine Rifle Model 1919, initially made up of overruns from the M1918 military production contract, was the first of several commercial Colt BARs that would follow. However, the high price of the weapon and its limited utility for most civilian owners resulted in few sales. Ad Topperwien ,
18630-669: The Colt Machine Rifles for sale abroad. All of the Colt automatic machine rifles, including the Colt Monitor, were available for export sale. After 1929 the Model 1925 and the Colt Monitor were available for export sale in Colt's exclusive sales territories per its agreement with FN. These Colt territories included North America, Central America, the West Indies, South America, Great Britain, Russia, Turkey, Siam (Thailand), India and Australia. A variant known as
18837-459: The Cutts compensator (a muzzle brake ) was offered as an attachment option for the Thompson. Models with the compensator were cataloged as No. 21AC , at the original price of $ 200. The plain Thompson (without the attachment) was designated No. 21A at a reduced price of $ 175. In 1928, Federal Laboratories took over distribution of the weapon from Thompson's Auto-Ordnance Corporation. The new cost
19044-508: The French were often second-rate or surplus and chambered in 8mm Lebel , further complicating logistics as machine gunners and infantrymen were issued different types of ammunition. Browning began to design the weapon later known as the BAR in 1910. He demonstrated the prototypes to the US military, which did not see an immediate use for the weapon until 1917. In 1917, prior to America's entry to
19251-487: The Korean War, US troops were surprised to encounter communist Chinese troops armed with Thompsons (amongst other captured US-made Nationalist Chinese and American firearms), especially during unexpected night-time assaults which became a prominent Chinese combat tactic in the conflict. The gun's ability to deliver large quantities of short-range automatic assault fire proved very useful in both defense and assault during
19458-464: The M1918 BAR's butt stock. The M1918A2's barrel was also fitted with a new flash suppressor and fully adjustable iron sights. Towards the end of the war a barrel-mounted carrying handle was added. Because of budget limitations initial M1918A2 production consisted of conversions of older M1918 BARs (remaining in surplus) along with a limited number of M1922s and M1918A1s. After the outbreak of war, attempts to ramp up new M1918A2 production were stymied by
19665-478: The M1918 as well, and by all accounts she was an excellent BAR operator. She used an M1918 on full-automatic to pin down unsuspecting law officers after they confronted the gang at a house in Joplin, Missouri . A Missouri highway patrolman at the scene, forced to dive for cover behind a substantial oak tree after Bonnie Parker opened up on him, later stated, "That little red-headed woman filled my face with splinters on
19872-545: The M1918 resulted in the M1922 machine rifle, adopted by the United States Cavalry in 1922 as a troop-level light machine gun. The weapon used a new heavy profile ribbed barrel, an adjustable spiked bipod (mounted to a swiveling collar on the barrel) with a rear, stock-mounted monopod, a side-mounted sling swivel and a new rear buttplate, fixed to the stock retaining sleeve. The hand guard was changed, and in 1926
20079-506: The M1928A1 units had complaints of the "L" 50-round drum magazine. The British Army criticized "the [magazine's] excessive weight, [and] the rattling sound they made" and shipped thousands back to the U.S. in exchange for 20-round box magazines. The Thompson had to be cocked, bolt retracted, ready to fire, in order to attach the drum magazine. The drum magazine also attached and detached by sliding sideways, which made magazine changes slow and cumbersome. They also created difficulty when clearing
20286-505: The M1928A1, and drum compatibility was not included in the design of the wartime M1 and M1A1 models. The Thompson was one of the earliest submachine guns to incorporate a double-column, staggered-feed box magazine design, which undoubtedly contributed to the gun's reputation for reliability. In addition, the gun performed better than most after exposure to rain, dirt, and mud. Blowback-operated Several blowback systems exist within this broad principle of operation, each distinguished by
20493-506: The M3/M3A1 never replaced the Thompson, and purchases continued until February 1944. Though the M3 was considerably cheaper to produce, at the end of World War II, the Thompson, with a total wartime production of over 1.5 million, outnumbered the M3/M3A1 submachine guns in service by nearly three to one. Thompson submachine guns were used by both sides during the 1948 Arab-Israeli war . Following
20700-596: The Mannlicher Model 1893 automatic rifle, the bolt in screw-delayed blowback uses a turn bolt that was delayed by angled interrupted threads delayed by a quarter twist to unlock. John T. Thompson designed an autorifle that operated on a similar principle around 1920 and submitted it for trials with the US Army. This rifle, submitted multiple times, competed unsuccessfully against the Pedersen rifle and Garand primer-actuated rifle in early testing to replace
20907-424: The Model of 1921. It was available to civilians, but, because of the weapon's high price, initially saw poor sales. The Thompson (with one Type XX 20 round "stick" magazine) had been priced at $ 200 in 1921 (roughly equivalent to $ 3,416 in 2023) The major initial complaints concerning the Thompson were its cumbersome weight, its inaccuracy at ranges over 50 yards (46 m), and its lack of penetrating power using
21114-499: The Model of 1928. The Thompson saw popularity as a point-defense weapon for countering ambushes by Nicaraguan guerrillas (in the Banana Wars ) and led to the creation of four-man fire teams which had as much firepower as a nine-man rifle squad. Federal sales were then followed by sales to police departments in the US, as well as to various international armies and constabulary forces; chiefly in Central and South America. In 1926,
21321-559: The StG 45 (M), had not progressed beyond the prototype stage by the end of World War II. After World War II, former Mauser engineers Ludwig Vorgrimler and Theodor Löffler perfected the mechanism between 1946 and 1950 while working for the French small arms manufacturer Centre d'Etudes et d'Armament de Mulhouse (CEAM). In 1950 Ludwig Vorgrimler was recruited to work for CETME in Spain. The first full-scale production rifle to utilize roller-delay
21528-549: The Swedish weapon has—apart from the different caliber—a spiked bipod and dust covers for ejection. The m/21 would become one of Sweden's main support weapons in the interwar years together with the water-cooled, belt-fed Ksp m/1914 medium machine gun (Swedish adaptation of the Austrian M07/12 ). Dissatisfied with the rapidly overheating fixed barrel of the m/21, Carl Gustaf began to design a new quick-detach mechanism for
21735-469: The Thompson as a limited-issue weapon, especially during their later island assaults. The Thompson was soon found to have limited effect in heavy jungle cover, where the low- velocity .45 bullet would not penetrate most small-diameter trees or protective armor vests. (In 1923, the Army had rejected the .45 Remington–Thompson , which had twice the energy of the .45 ACP.) In the U.S. Army, many Pacific War jungle patrols were originally equipped with Thompsons in
21942-460: The Thompson in small quantities for use by their armies and militias. In the 1930s, Taiyuan Arsenal (a Chinese weapons manufacturer) produced copies of the Thompson for Yan Xishan , the then warlord of Shanxi province. The FBI had also acquired Thompsons in 1933 following the Kansas City Massacre . A number of these guns were acquired by a construction company in Brazil, after construction of
22149-468: The Thompson was the only submachine gun available to the Australian Army for most of the vital Kokoda Track campaign in 1942. It became so prized that soldiers routinely picked up Thompson guns dropped by killed or wounded comrades. However, the weight of the ammunition and difficulties in supply eventually led to its replacement in Australian Army units in 1943 by Australian-made submachine guns,
22356-484: The U.S. and South Korean military, even though the Thompson had been replaced as standard-issue by the M3/M3A1. With huge numbers of guns available in army ordnance arsenals, the Thompson remained classed as Limited Standard or Substitute Standard long after the standardization of the M3/M3A1. Many Thompsons were distributed to the US-backed Nationalist Chinese armed forces as military aid before
22563-427: The US Army. The army specified a need for a BAR designed to serve in the role of a light machine gun for squad-level support fire. Early prototypes were fitted with barrel-mounted bipods as well as pistol grip housings and a unique rate-of-fire reducer mechanism purchased from FN Herstal . The rate reducer mechanism performed well in trials, and the pistol grip housing enabled the operator to fire more comfortably from
22770-460: The United States in the 1920s. It was a common sight in the media at the time, and was used by both law enforcement officers and criminals. The Thompson was widely adopted by the U.S. armed forces during World War II , and was also used extensively by other Allied troops during the war. Its main models were designated as the M1928A1, M1 and M1A1 during this time. More than 1.5 million Thompson submachine guns were produced during World War II. It
22977-478: The action in which it was used. During the failed 1924 Estonian coup , communists used Thompsons in an attempt to storm the Tallinn barracks; meanwhile the MP 18 was used by the defenders. This was possibly the first engagement where submachine guns were used on both sides. The Thompson achieved early notoriety in the hands of Prohibition and Great Depression -era gangsters and the lawmen who pursued them. It
23184-633: The agency. Some of the FBI's Monitors were distributed to field offices for use as support weapons if needed on a particular operation, while the remainder were retained at the FBI Academy in Quantico, Virginia , for training purposes. Colt sold an additional 11 Colt Monitors to the US Treasury Department in 1934, while 24 guns were sold to state prisons, banks, security companies and accredited city, county and state police departments. At least one member of
23391-464: The aid of a shoulder stock; and these factors help to ameliorate the disruption to the shooter's aim caused by the heavy bolt's movement. Consequently, simple blowback is adequate for somewhat more powerful rounds in submachine guns than in standard pistols. One of the very few known simple blowback firearms capable of firing fully powered rifle cartridges was the Brixia 930 light machine gun, that required
23598-507: The alternative to API is some system of delayed or retarded blowback, in which the bolt is never fully locked, but is initially held in place, sealing the cartridge in the chamber by the mechanical resistance of one of various designs of delaying mechanism. As with the resistance provided by momentum in API, it takes a fraction of a second for the propellant gases to overcome this and start moving cartridge and bolt backwards; this very brief delay
23805-495: The ambush team that killed Bonnie and Clyde was armed with a Colt Monitor. Although it has sometimes been alleged that the M1918 or M1918A2 BAR was used by members of the Symbionese Liberation Army (SLA) in a shootout with Los Angeles police on May 17, 1974, no SLA members ever used such a weapon. The confusion arose out of Browning's decision in the 1970s to also designate its semi-automatic hunting rifle
24012-413: The arm to various propellant and projectile specific pressure behavior. Their reliable functioning is limited by specific ammunition and arm parameters like bullet weight, propellant charge, barrel length and amount of wear. At the moment of cartridge ignition the chamber has to be and remain sealed, until the bullet has exited the barrel and the gas pressure within the bore has dropped to a safe level before
24219-415: The barrel and pressures have dropped to a safe level. This mechanism was used on the Pedersen rifle and Schwarzlose MG M.07/12 machine gun. John Browning developed this simple method whereby the axis of bolt movement was not in line with that of the bore probably during late WWI and patented it in 1921. The result was that a small rearward movement of the bolt in relation to the bore-axis required
24426-461: The barrel that mates the externally grooved chamber to a series of rotating flanges in the receiver operated by a locking lever. The barrel also received cooling fins along its entire length. These enhancements were incorporated into the fm/1935 prototype, which was favorably evaluated during trials in 1935. The final version was the Kg m/37, adopted for service in 1937, which uses a smooth-contour, unfinned barrel. Numerous m/21 guns were retrofitted with
24633-400: The bearings. Bearing delay is designed to be tuned based on the user's preference or configuration of other components by swapping to a lifter with a different geometry. The bearing delay design is described in U.S. patent 11,371,789 , U.S. patent 11,543,195 , U.S. patent 11,781,824 , and U.S. patent 12,146,717 . Lever-delayed blowback utilizes leverage to put the bolt at
24840-660: The bolt carrier does not rebound. Due to the relative low bolt thrust exhibited by pistol cartridges the anti-bounce mechanism is omitted by Heckler & Koch on their roller-delayed blowback firearms chambered for pistols cartridges. Heckler & Koch's MP5 submachine gun is the most common weapon still in service worldwide using this system. The Heckler & Koch P9 semi-automatic pistol, CETME Ameli light machine gun, SIG MG 710-3 , Heckler & Koch HK21 and Ohio Ordnance REAPR general-purpose machine guns also use it. Roller-delayed blowback arms are ammunition specific, since they lack an adjustable gas port or valve to adjust
25047-420: The bolt carrier, slowing the speed of the bolt head. This delay allows pressure to drop prior to extraction without the penalty of a heavier bolt carrier assembly. The system is similar to roller and lever-delayed blowback in that it uses the mass of the bolt carrier moving at a faster rate than the bolt head to delay the action from opening. The design is described in U.S. patent 10,436,530 . First used on
25254-480: The bolt gap and push the locking piece forward. Installing smaller diameter rollers results in the reverse effects. Bearing delay blowback uses a plurality of ball bearings to delay the movement of the bolt carrier group after firing. MEAN introduced Bearing delay blowback in 2023 with their Bearing Delay Upper Receiver chambered in 9×19mm Parabellum. This system uses the movement of three ball bearings arranged approximately 120° apart from one another that move in
25461-429: The bolt head. The primary advantage of roller-delayed blowback is the simplicity of the design compared to gas or recoil operation. The roller-delayed blowback firearm action was patented by Mauser's Wilhelm Stähle and Ludwig Vorgrimler . Though appearing simple, its development during World War II was a hard technical and personal effort, as German engineering, mathematical and other scientists had to work together on
25668-490: The bolt safely closed. The box magazine was quickly attached and detached, and was removed downward, making clearing jams easier. The box magazine tripped the bolt open lock when empty, facilitating magazine changes. An empty box was easy to reload with loose rounds. However, users complained that it was limited in capacity. In the field, some soldiers would tape two "XX" magazines together, in what would be known as "jungle style" , to quicken magazine changes. Two alternatives to
25875-426: The bolt-bounce problem. With these angles the geometrical transmission ratio of the bolt carrier to the bolthead became 3:1, so the rear bolt carrier was forced to move 3 times faster than the bolthead. The rearward forces on the bolt carrier and receiver were 2:1. The force and impulse transmitted to the receiver increases with the force and impulse transmitted to the bolt carrier. Making the bolt carrier heavier lessens
26082-482: The bolt. Because the forward and rearward speeds of the bolt tend to be approximately the same, the API blowback allows the weight of the bolt to be halved. Because the momentum of the two opposed bolt motions cancels out over time, the API blowback design results in reduced recoil. Advanced primer ignition (API) was originally developed by Reinhold Becker for use on the Becker Type M2 20 mm cannon . It became
26289-482: The bore through a piston—about 5 ms in the Dragunov sniper rifle , which used the same cartridge as Mamontov's rifle. Barishev made a fully automatic, but rather bulky mechanism that used a mechanical delay. In his system, the case cartridge pushed back a tilting bolt face, that upon reaching a certain angle pushes backwards an unlocking lever that continues farther before unlocking the bolt. The GRAU however still gave
26496-457: The breech remains locked. This allows chamber pressure to drop to safe levels once the bullet departs the barrel. The continuing motion of the slide lifts the breech block from its recess and pulls it rearward, continuing the firing cycle. Straight-walled cartridges are used in this operation as they are less prone to rupturing than tapered (conical) cartridges in firearms with bolt operations that instantly retract rounds when under high pressure from
26703-439: The cartridge itself). The last part of forward motion and the first part of the rearward motion of the case and bolt happen within the confines of this extended chamber. As long as the gas pressure in the barrel is high, the walls of the case remain supported and the breach sealed, although the case is sliding rearwards. This sliding motion of the case, while it is expanded by a high internal gas pressure, risks tearing it apart, and
26910-743: The case and slide, reducing their mass requirements. The first known use of the system was on the Fritz Mann pistol in 1920 and later on the High Standard Corp model T3 experimental pistol developed by Ott-Helmuth von Lossnitzer while working for High Standard. Other firearms that used this system were the LWS Seecamp pistol, the AMT Automag II, and the Kimball .30 Carbine pistol. The SIG SG 510 rifle family incorporates
27117-404: The chamber when firing. The Pedersen Remington Model 51 pistol, SIG MKMO submachine gun and R51 pistol are the only production firearms to have used this design. Flywheel delayed blowback operation is where, during firing, the bolt opening is delayed by the rotational inertia of a flywheel. This is driven by a rack and pinion arrangement on the bolt carrier. The Barnitzke , Kazachok SMG, and
27324-435: The chamber, will undergo a degree of blowback action. The energy from the expansion of gases upon firing appears in the form of kinetic energy transmitted to the bolt mechanism, which is controlled and used to operate the firearm's operation cycle. The extent to which blowback is employed largely depends on the manner used to control the movement of the bolt and the proportion of energy drawn from other systems of operation. How
27531-399: The chamber. When the cartridge is fired, the front of the floating chamber is thrust back by gas pressure impinging on the front of the chamber as in a traditional piston. This, added to the blowback energy imparted on the cartridge, pushes the bolt back with greater energy than either force alone. Often described as "accelerated blowback", this amplifies the otherwise anemic recoil energy of
27738-422: The changes reduced the rate of fire from 800 to the 600 rpm of the U.S. Navy Model 1928. Later M1 and M1A1 Thompsons averaged also 600 rpm. Compared to more modern submachine guns, the Thompson is quite heavy, weighing roughly the same as the contemporary M1 Garand semi-automatic rifle, and requires a lot of cleaning. This was one of the major complaints about the weapon by U.S. Army personnel to whom it
27945-542: The complexity of a recoil or gas-operated reloading mechanism. Blish's design (then known as the Blish lock ) was based on the supposed adhesion of inclined metal surfaces under pressure. Thompson gained financial backing from the businessman Thomas F. Ryan and proceeded to found a company, which he named the Auto-Ordnance Company , in 1916, for the purpose of developing his new "auto rifle". The Thompson
28152-617: The course of patrol and gunboat duty along the Yangtze River in China. The First Marine Brigade stationed in Port-au-Prince , Haiti, noted that training a man to use the BAR proficiently took a full two days of range practice and instruction, compared to half a day with the .45 caliber Thompson submachine gun. Prior to World War II, both the US Army and Marine Corps had a separate BAR squad together with three rifle squads in
28359-564: The discovery that the World War I tooling used to produce the M1918 was either worn out or incompatible with modern production machinery. New production was first undertaken at the New England Small Arms Corp. and International Business Machines Corp. (a total of 188,380 new weapons were manufactured). In 1942 a shortage of black walnut for butt stocks and grips led to the development of a black plastic butt stock for
28566-474: The early part of the war when it was constantly mobile and shifting back and forth. Many Chinese Thompsons were captured and placed into service with American soldiers and marines for the remaining period of the war. The Yugoslav Army received 34,000 M1A1 Thompsons during the 1950s as part of a US Military Aid to Yugoslavia Agreement. These guns were used during the Yugoslav Wars in the 1990s. During
28773-518: The early phases of the New Guinea and Guadalcanal campaigns, but soon began employing the Browning Automatic Rifle in its place as a point defense weapon. The Army introduced the U.S. M3 and M3A1 submachine guns in 1943 with plans to produce the latter in numbers sufficient to cancel future orders for the Thompson, while gradually withdrawing it from first-line service. However, due to unforeseen production delays and requests for modifications,
28980-477: The energy of primer setback to unlock and cycle the firearm. John Garand developed the system in an unsuccessful bid to replace the M1903 bolt-action rifle in the early 1920s. Garand's prototypes worked well with US military .30-06 ammunition and uncrimped primers, but then the military changed from a fast burning gunpowder to a progressive burning Improved Military Rifle (IMR) powder. The slower pressure rise made
29187-467: The fall of Chiang Kai-shek 's government to Mao Zedong 's communist forces at the end of the Chinese Civil War in 1949 (Thompsons had already been widely used throughout China since the 1920s, at a time when several Chinese warlords and their military factions running various parts of the fragmented country made purchases of the weapon and then subsequently produced many local copies). During
29394-624: The first time on 13 September 1918. The weapon was personally demonstrated against the enemy by 2nd Lt. Val Allen Browning , the inventor's son. Despite being introduced very late in the war, the BAR made an impact disproportionate to its numbers; it was used extensively during the Meuse-Argonne Offensive and made a significant impression on the Allies (France alone requested 15,000 automatic rifles to replace their Chauchat machine rifles). US Marines briefly took possession of
29601-423: The force required to compress the action spring. The design must ensure that the delay is long enough that the bullet exits the barrel before the cartridge case clears the chamber. The empty case is ejected as the bolt travels to the rear. The stored energy of the compressed action spring then drives the bolt forward (although not until the trigger is pulled if the weapon fires from an open bolt ). A new cartridge
29808-400: The front outer surface of the cartridge case and its interior and thus ensures extraction without tearing the case making extraction easier and more reliable. In 1944 other German companies like Großfuß (de) , Rheinmetall and C.G. Haenel showed interest in developing roller-delayed blowback small arms. Großfuß worked on a roller-delayed blowback MG 45 general-purpose machine gun that, like
30015-417: The gas pressure slightly longer until it reaches a safe level to extract. This operation is almost similar to a simple blowback operation, API blowback firearms that have fired the round at the point where the cartridge is fully chambered operate in a similar way. For more powerful rounds that cannot be safely used in simple blowback, or in order to obtain a lighter mechanism than the simple format can provide,
30222-600: The government but kept hidden and were later used by the Democratic Army of Greece. The Thompson also found service with the KNIL and the Netherlands Marine Corps during their attempt to retake their former colony of Indonesia. The gun was used by Indonesian infiltrators during the 1965 Indonesia–Malaysia confrontation . By the time of the Korean War in 1950, the Thompson had seen much use by
30429-545: The gun is tilted up. Due to the required bolt weight, blowback designs in pistols are generally limited to calibers smaller than 9×19mm Parabellum (e.g., .25 ACP , .32 ACP , .380 ACP , 9×18mm Makarov , etc.) There are exceptions such as the simple blowback pistols from Hi-Point Firearms which include models chambered in .40 S&W and .45 ACP . Simple blowback operation can also be found in small-bore (such as .22LR ) semi-automatic rifles , carbines and submachine guns . Most simple blowback rifles are chambered for
30636-600: The gun was widely utilized in British and Canadian commando units, as well as in the U.S. Army paratrooper and Ranger battalions , where it was issued more frequently than in line infantry units because of its high rate of fire and its stopping power, which made it very effective in the kinds of close combat these special operations troops were expected to undertake. Military Police were fond of it, as were paratroopers, who "borrowed" Thompsons from members of mortar squads for use on patrols behind enemy lines. The gun
30843-550: The gun, resulting in a new MG FF/M model with ammunition not being interchangeable between the two models. The 30 mm MK 108 cannon was perhaps the apogee of API blowback technology during World War II. The principle is also used in some automatic grenade launchers, for example in the US Mk 19 grenade launcher or Russian AGS-30 . A closed bolt firing equivalent of Advanced Primer Ignition that uses straight-sided rebated rim cartridges in an extended deeper chambering to contain
31050-426: The larger sense, blowback might well be considered a special form of gas operation. This is reasonable because the cartridge case may be conceived of as a sort of piston driven by the powder gases. Actually, blowback involves so many special problems that it is best considered to be in a class by itself. The question whether or not it should be included within the more general class of gas operation or recoil operation
31257-415: The loading of another cartridge, is derived from the inertia of the spent cartridge case being pushed out the rear of the chamber by rapidly expanding gases produced by a burning propellant, typically gunpowder. When a projectile (e.g. bullet ) is still within the gun barrel , the high-pressure propellant gas behind it is contained within what could be seen as a closed system ; but at the moment it exits
31464-691: The mail from a spate of robberies. These weapons were loaned to the United States Marine Corps which was, at that time, tasked with guarding mail shipments; this prompted the US Navy to formally test the Thompson. The Navy requested a reduction in the rate of fire. Auto-Ordnance complied, modifying the weapons by adding a substantial amount of mass to the actuator. In 1927 a number of Thompsons would be shipped to Marines in China and Nicaragua . The Navy subsequently ordered 500 guns, designated
31671-462: The methods used to control bolt movement. In most actions that use blowback operation, the breech is not locked mechanically at the time of firing: the inertia of the bolt and recoil spring(s), relative to the weight of the bullet, delay opening of the breech until the bullet has left the barrel. A few locked breech designs use a form of blowback (example: primer actuation) to perform the unlocking function. The blowback principle may be considered
31878-427: The most basic auto loading operation type. In a blowback mechanism, the bolt rests against the rear of the barrel, but is not locked in place. At the point of ignition, expanding gases push the bullet forward through the barrel while at the same time pushing the case rearward against the bolt. The expanding gases push the bolt assembly to the rear, but the motion is slowed by the mass of the bolt, internal friction, and
32085-405: The movement of the bolt is controlled is where blowback systems differ. Blowback operation is most often divided into three categories, all using residual pressure to complete the cycle of operation: "simple blowback" (often just "blowback"), "delayed/retarded blowback", and "advanced primer ignition". Relating blowback to other types of automatic firearm operation, George M. Chinn wrote that: "In
32292-410: The opening velocity of the bolt. The extremely high bolt carrier velocities problem was not solved by trial and error. Mathematician Karl Maier provided analysis of the components and assemblies in the development project. In December 1943 Maier came up with an equation that engineers used to change the angles in the receiver to 45° and 27° on the locking piece relative to the longitudinal axis reducing
32499-575: The ordnance department of the U.S. Army , was the original inventor and developer of the Thompson submachine gun. He envisioned it as being a fully automatic rifle in order to replace the bolt-action service rifles then in use (such as the American M1903 Springfield ). Thompson came across a patent issued to the American inventor John Bell Blish in 1915, while searching for a way to allow his weapon to operate safely without
32706-416: The other side of that tree with one of those damned guns." As the use of automatic weapons by criminal elements in the US became more widespread, FBI Director J. Edgar Hoover ordered the agency to acquire and commence regular training with automatic shoulder weapons, including the Thompson submachine gun and the BAR. For its BARs the FBI turned to Colt, which sold 90 Colt Monitor automatic machine rifles to
32913-415: The other two types: API or delayed blowback. In the API blowback design, the primer is ignited when the bolt is still moving forward and before the cartridge is fully chambered (akin to the fire- out-of-battery principle used in some mountain guns like Canon de 65 M (montagne) modele 1906 , although there the bolt is locked and whole ordnance is moving at fire). This requires a very careful design to ensure
33120-504: The price of a black-market Colt Monitor was $ 5,000, with military BARs going for somewhat less. The army's M1918 was a favorite of gangster Clyde Barrow , who obtained his through periodic robberies of Army National Guard armories in the Midwest. Barrow liked to use armor-piercing (AP) .30-06 ammunition he obtained from armory stores, and frequently modified his BARs to suit his own needs. Barrow taught his girlfriend Bonnie Parker to fire
33327-675: The primer actuated prototypes unreliable, so Garand abandoned the design for a gas operated rifle that became the M1 Garand . AAI Corporation used a primer piston in a rifle submitted for the SPIW competition. Other rifles to use this system were the Postnikov APT and Clarke carbine as described in U.S. patent 2,401,616 . A similar system is used in the spotting rifles on the LAW 80 and Shoulder-launched Multipurpose Assault Weapon use
33534-466: The procurement of 10,000 wz. 1928 light machine guns chambered in 7.92×57mm Mauser, which are similar to the R75 variant but designed specifically to meet the requirements of the Polish army. Changes to the base design include a pistol grip, different type of bipod, open-type V-notch rear sight and a slightly longer barrel. Subsequent rifles were assembled in Poland under license by the state rifle factory (Państwowa Fabryka Karabinów) in Warsaw. The wz. 1928
33741-473: The prone position. However, in 1939 the army declared that all modifications to the basic BAR be capable of being retrofitted to earlier M1918 guns with no loss of parts interchangeability. This effectively killed the FN-designed pistol grip and its proven rate reducer mechanism for the new M1918 replacement. The final development of the M1918A2 was authorized on 30 June 1938. The FN-designed pistol grip and rate-reducer mechanism with two rates of automatic fire
33948-404: The proper balance and equalization of forces between the projectile weight, propellant charge, barrel length, bolt weight, and return spring strength. In a simple blowback design, the propellant gases have to overcome static inertia to accelerate the bolt rearwards to open the breech. In an API blowback, they first have to do the work of overcoming forward momentum to arrest the forward motion of
34155-477: The receiver and force the round into the feed path during unlocking. The machine gun was accepted in 1937 and ordered by the Polish Air Force as the karabin maszynowy obserwatora wz. 1937 ("observers machine gun model 1937"). Eventually 339 machine guns were acquired and used as armament in the PZL.37 Łoś medium bomber and the LWS-3 Mewa reconnaissance aircraft. In 1920, Belgian arms manufacturer Fabrique Nationale (FN) acquired sales and production rights to
34362-404: The recoil impact. [...] The exacting requirements in design and construction of gun and ammunition reduce this type almost to the point of academic interest only." API mechanisms are very sensitive to the ammunition used. For example, when the Germans switched their MG FF (an Oerlikon FFF derivative) to their new, lighter mine shell , they had to rebalance the spring strength and bolt weight of
34569-416: The recoil velocity. For Mausers StG 45(M) project Maier assumed a 120 g (4.2 oz) bolt head and 360 g (12.7 oz) bolt carrier (1 to 3 ratio). The prototype StG 45 (M) assault rifle had 18 longitudinal gas relief flutes cut in the chamber wall to assist the bloated cartridge casing from the chamber walls during extraction. Fluting the end of the chamber provides pressure equalization between
34776-439: The region. Some of the first batches of Thompsons were bought (in America) by agents of the Irish Republic (notably the Irish politician Harry Boland ). The first test of the Thompson in Ireland was performed by Irish Republican Army unit commander Tom Barry , of the West Cork Brigade , in the presence of IRA leader Michael Collins . They purchased a total of 653 units, though US customs authorities in New York seized 495 of
34983-406: The replacement of the iron sights with a smaller version and reshaping the butt to a fish tail. In the mid-1930s, Polish small-arms designer Wawrzyniec Lewandowski was tasked with developing a flexible aircraft-mounted machine gun based on the Browning wz.1928. This resulted in the wz. 1937. Changes included increasing the weapon's rate of fire to 1,100 rounds/min, eliminating the butt stock, adding
35190-445: The rest went to various state prisons, banks, security companies and accredited police departments. Although available for export sale, no examples appear to have been exported. In 1932, a greatly shortened version designed for bush warfare was developed by USMC Maj. H.L. Smith and was the subject of an evaluative report by Capt. Merritt A. Edson , ordnance officer at the Quartermaster's Depot in Philadelphia, Pennsylvania. The barrel
35397-438: The screw-on receiver extension and quick-change barrel and renamed the Kg m/21-37. The m/37 remained in service until replaced by the FN MAG, but was still in second-line use until 1980. Carl Gustaf also developed a belt-fed prototype; however, it was never adopted. The Chinese Nationalist Army used the FN Mle 1930 throughout the Second Sino-Japanese War . 29,550 were bought from Belgium between 1933 and 1939. The Chinese BAR
35604-436: The seal is broken and chamber starts to open. For obtaining a proper and safe functioning parameters bandwidth arms manufactures offer a variety of locking pieces with different mass and shoulder angles and cylindrical rollers with different diameters. The angles are critical and determine the unlock timing and gas pressure drop management as the locking piece acts in unison with the bolt head carrier. The bolt gap width determines
35811-502: The simplified World War II M1 and M1A1 variants (without the Blish lock and oiling system). A Model 1921A believed to have been owned by Bonnie and Clyde , but without historical documentation to substantiate this provenance, sold at auction on 21 January 2012, in Kansas City for $ 130,000. Early versions of the Thompson, the Model 1919, had a fairly high cyclic rate of fire, as high as 1,200 rounds per minute (rpm), with most Model 1921s at 800 rpm. This rate of fire, combined with
36018-464: The units in June 1921. The remainder found their way to the Irish Republican Army by way of Liverpool, England, and were used in the last month of the Irish War of Independence (1919–1921). After a truce with the British in July 1921, the Irish Republican Army imported more units, which were used in the subsequent Irish Civil War (1922–1923). The Thompson was not found to be very effective in Ireland; having only caused serious casualties in 32 percent of
36225-414: The use of more powerful ammunition in a lighter gun than would be achieved by using simple blowback, and the reduction of felt recoil results in further weight savings. The original Becker cannon, firing 20×70mmRB ammunition, was developed to be carried by World War I aircraft, and weighed only 30 kg. Oerlikon even produced an anti-tank rifle firing 20×110mmRB ammunition using the API blowback operation,
36432-480: The war as a slightly lighter alternative to the M1918A2. Production rates greatly increased in 1943, after IBM introduced a method of casting BAR receivers from a new type of malleable iron developed by the Saginaw division of General Motors , called ArmaSteel . After it successfully passed a series of tests at Springfield Armory, the Chief of Ordnance instructed other BAR receiver manufacturers to change over from steel to ArmaSteel castings for this part. During
36639-406: The war ended two days before prototypes could be shipped to Europe. At an Auto-Ordnance board meeting in 1919, in order to discuss the marketing of the "Annihilator", with the war now over the weapon was officially renamed the "Thompson Submachine Gun". While other weapons had been developed shortly prior with similar objectives in mind, the Thompson was the first weapon to be labeled and marketed as
36846-422: The war, John Browning personally brought to Washington, D.C. two types of automatic weapons for the purposes of demonstration: a water-cooled machine gun (later adopted as the M1917 Browning machine gun ) and a shoulder-fired automatic rifle known then as the Browning Machine Rifle or BMR , both chambered for the standard US .30-06 Springfield (7.62×63mm) cartridge. Colt and the Ordnance Department arranged for
37053-400: The war, Thompsons were issued to members of Israel's elite Unit 101 , upon the formation of that unit in 1953. During the Greek Civil War , the Thompson submachine gun was used by both sides. The Hellenic Armed Forces , gendarmerie and police units were equipped with Thompson submachine guns supplied by the British and later in the war by the United States. The opposing Communist fighters of
37260-402: Was accepted into service with the Polish army in 1927 under the formal name 7,92 mm rkm Browning wz. 1928 and—until the outbreak of World War II—was the primary light support weapon of Polish infantry and cavalry formations (in 1939 Poland had a total of approximately 20,000 wz. 1928 rifles in service). Additional detail modifications were introduced on the production line; among them were
37467-441: Was also depicted in gangster films during this era, most notably regarding the Saint Valentine's Day Massacre . The Thompson guns used in the massacre are still being held by the Berrien County Sheriff's Department. The Thompson has been referred to by one researcher as the "gun that made the twenties roar ". Around 200 Model of 1921 Thompsons were sold in 1926 to the United States Postal Inspection Service so they could protect
37674-465: Was also standard issue to US naval landing forces during the period. The weapon was a standard item in US warship armories, and each BAR was accompanied by a spare barrel. Large capital ships often had over 200 BARs on board, with many of the US Navy BARs remaining in service well into the 1960s. The BAR also saw action with US Marine Corps units participating in the Haitian and Nicaraguan interventions, as well as with US Navy shipboard personnel in
37881-444: Was announced on 6 April 1917, the high command was made aware that to fight this trench war , dominated by machine-guns, they had on hand a mere 670 M1909 Benét–Merciés , 282 M1904 Maxims and 158 Colt-Browning M1895s . After much debate, it was finally agreed that a rapid rearmament with domestic weapons would be required, but until that time, US troops would be issued whatever the French and British had to offer. The arms donated by
38088-420: Was based on the concept of "walking fire", a French practice in use since 1916 for which the CSRG 1915 ( Chauchat ) had been used accompanying advancing squads of riflemen toward the enemy trenches, as regular machine guns were too cumbersome to move with the troops during an assault. In addition to shoulder-fired operation, BAR gunners were issued a belt with magazine pouches for the BAR and sidearm along with
38295-433: Was chambered for the German 7.92×57mm Mauser round, the standard rifle cartridge of the National Revolutionary Army . After the outbreak of the Pacific War , the Chinese Expeditionary Army in Burma was equipped with American BARs. Towards the end of World War II, small quantities of American equipment, including the BAR, made their way into mainland China. With the cessation of WWI hostilities, Colt Arms Co. received
38502-496: Was contracted by the Auto-Ordnance Corporation to manufacture the initial mass production of 15,000 Thompson Submachine Guns in 1920. An original Colt Model 1921 A or AC, Model 1927 A or AC, Model 1928 Navy A or AC, properly registered in working condition with original components can easily fetch from US$ 25,000 to $ 45,000+ depending on condition and accessories. For WWII, approximately 1,700,000 Thompson Submachine Guns were produced by Auto-Ordnance and Savage Arms , with 1,387,134 being
38709-452: Was denied and the Winchester Repeating Arms Company (WRAC) was designated as the prime contractor. Winchester gave valuable assistance in refining the BAR's final design, correcting the drawings in preparation for mass production. Among the changes made, the ejection pattern was modified (spent casings were directed to the right side of the weapon instead of straight up). Since work on the weapon did not begin until February 1918, so hurried
38916-408: Was designed to be carried by infantrymen during an assault advance while supported by the sling over the shoulder, or to be fired from the hip. This is a concept called " walking fire "—thought to be necessary for the individual soldier during trench warfare. The BAR never entirely lived up to the original hopes of the War Department as either a rifle or a machine gun. The US Army, in practice, used
39123-436: Was done on the project. The M1918A1, featuring a lightweight spiked bipod with a leg height adjustment feature attached to the gas cylinder and a hinged steel butt plate, was formally approved on 24 June 1937. The M1918A1 was intended to increase the weapon's effectiveness and controllability firing in bursts. Relatively few M1918s were rebuilt to the new M1918A1 standard. In April 1938, work commenced on an improved BAR for
39330-411: Was first used in Mauser 's Gerät 06H prototype. Roller-delayed blowback operation differs from roller-locked recoil operation as seen in the MG 42 and gas operated roller locked, as seen in the Gerät 03 and Gerät 06 . Unlike the MG 42, in roller-delayed blowback the barrel is fixed and does not recoil, and unlike the Gerät 03 and Gerät 06 and StG 44, roller-delayed blowback systems lack
39537-452: Was found that the only cartridge then in service suitable for use with the new lock was the .45 ACP . General Thompson envisioned a "one-man, hand-held machine gun" chambered in .45 ACP to be used as a "trench broom" for the ongoing trench warfare of World War I . Oscar V. Payne designed the new firearm along with its stick and drum magazines. The project was titled "Annihilator I". Most of the design issues had been resolved by 1918; however,
39744-440: Was issued as the sole automatic fire support for a twelve-man squad, and all men were trained at the basic level how to operate and fire the weapon in case the designated operators were killed or wounded. At the start of the war, infantry companies designated three-man BAR teams, a gunner, an assistant gunner, and an ammunition bearer who carried additional magazines for the gun. By 1944, some units were using one-man BAR "teams" with
39951-426: Was issued. Although the drum magazine provided significant firepower, in military service it was found to be overly heavy and bulky, especially when slung on the shoulder while marching. The M1928A1 Thompson drum magazine was rather fragile, and cartridges tended to rattle inside it, producing unwanted noise. For these reasons, the 20-round and later 30-round box magazines soon proved most popular with military users of
40158-501: Was less accurate when fired from the shoulder, and had a loud report combined with a fierce muzzle blast. Attaching a Cutts compensator materially reduced the muzzle blast, but this was more than offset by the increase in smoke and dust at the muzzle when fired, obscuring the operator's vision. Nor did it improve control of the weapon when fired in bursts of automatic fire. Though the report recommended building six of these short-barreled jungle BARs for further evaluation, no further work
40365-499: Was listed as $ 225 per weapon (equivalent to $ 3,992 in 2023), with $ 5 per 50-round drum and $ 3 per 20-round magazine. Thompsons had also been widely used throughout China, where several Chinese warlords and their military factions running various parts of the fragmented country made purchases of the weapon, and subsequently produced many local copies. Nationalist China acquired a substantial number of Thompson guns for use against Japanese land forces. They began producing copies of
40572-422: Was not widespread. In the Malayan Campaign , the Burma Campaign and the Pacific Theater , Lend-Lease-issue Thompsons were used by the British Army , Indian Army , Australian Army infantry and other Commonwealth forces. They used the Thompson extensively in jungle patrols and ambushes, where it was prized for its firepower, though it was criticized for its hefty weight and poor reliability. In New Guinea,
40779-483: Was partially replaced by the MAC-10 , albeit during Vietnam, the fully automatic fire provided by the M16 made the Thompson less effective than it previously had been. Still, not only did some U.S. soldiers have use of them in Vietnam, they encountered them as well. The Viet Cong liked the weapon and used both captured models as well as manufacturing their own copies in small jungle workshops. The Australian government destroyed most of their Thompson machine carbines in
40986-436: Was patented by Henry Bessemer . In 1856 a crank-operated cannon with a blowback-operated cocking mechanism was patented in the US by Charles E. Barnes. In 1876 a single-shot breech-loading rifle with an automatic breech-opening and cocking mechanism using a form of blowback was patented in Britain and America by the American Bernard Fasoldt. In 1883 Hiram Maxim patented a blowback-operated rifle. In 1884 he would also patent
41193-406: Was primarily developed in Cleveland, Ohio . Its principal designers were Theodore H. Eickhoff, Oscar V. Payne, and George E. Goll. By late 1917, the limits of the Blish lock were discovered (which is essentially an extreme manifestation of static friction ), and, rather than the firearm working as a locked breech, the weapon was instead designed to function as a friction-delayed blowback action. It
41400-423: Was prized by those lucky enough to get one and proved itself in the close street fighting that was encountered frequently during the invasion of France. A Swedish variant of the M1928A1, the Kulsprutepistol m/40 (machine pistol, model 40), served in the Swedish Army between 1940 and 1951. Through Lend-Lease , the Soviet Union also received the Thompson, but due to a shortage of appropriate ammunition, its use
41607-493: Was produced in various calibers, including .30-06 Springfield (7.62×63mm), 7.65×53mm Belgian Mauser , 7×57mm Mauser , 7.92×57mm Mauser , and .303 British (7.7×56mmR) (no Colt-manufactured Model 1925 rifles in 6.5×55mm appear to have been sold). A minor variant of the Model 1925 (R75) was the R75A light machine gun with a quick-change barrel (produced in 1942 in small quantities for the Dutch army ). Between 1921 and 1928 FN Herstal imported over 800 Colt-manufactured examples of
41814-409: Was shelved in favor of a rate-reducer mechanism designed by Springfield Armory, and housed in the butt stock. The Springfield Armory rate reducer also provided two selectable rates of fully automatic fire only, activated by engaging the selector toggle. Additionally, a skid-footed bipod was fitted to the muzzle end of the barrel, magazine guides were added to the front of the trigger guard, the hand guard
42021-409: Was shortened nine inches (229 mm) at the muzzle and the gas port and gas cylinder tube were relocated. The modified BAR weighed 13 lb 12 oz (6.24 kg) and was only 34.5 inches (880 mm) long overall. Though it proved superior to the M1918 in accuracy when fired prone in automatic mode and equal in accuracy to the standard M1918 at ranges of 500–600 yards (460–550 m) from a rest, it
42228-441: Was shortened, a heat shield was added to help the cooling process, a small separate stock rest (monopod) was included for attachment to the butt and the weapon's role was changed to that of a squad light machine gun. The BAR's rear sight scales were also modified to accommodate the newly standardized M2 ball ammunition with its lighter, flat-base bullet. The M1918A2's walnut butt stock is approximately one inch (2.5 cm) longer than
42435-494: Was the Model DA1 chambered for the 7.62×51mm NATO cartridge and feeding from the 20-round magazines for the FN FAL battle rifle. In 1922, the French Army considered the introduction of the BAR or of the Fusil-mitrailleur MAS modèle 1922 , a copy of the BAR produced by the Manufacture d'armes de Saint-Étienne . The FM 24/29 light machine gun was eventually adopted. Production of the BAR in Belgium began only after signing an agreement with Poland (on 10 December 1927) involving
42642-528: Was the Spanish CETME battle rifle , which was closely followed by the Swiss SIG SG 510 and the CETME Model B-based Heckler & Koch G3 . The G3 bolt features an anti-bounce mechanism that prevents the bolt from bouncing off the barrel's breech surface. The G3's "bolt head locking lever" is a spring-loaded claw mounted on the bolt carrier that grabs the bolt head as the bolt carrier group goes into battery. The lever essentially ratchets into place with friction, providing enough resistance to being re-opened that
42849-665: Was the schedule at Winchester to bring the BAR into full production that the first production batch of 1,800 rifles was delivered out of spec; it was discovered that many components did not interchange between rifles, and production was temporarily halted until manufacturing procedures were upgraded to bring the weapon up to specifications. The initial contract with Winchester called for 25,000 BARs. They were in full production by June 1918, delivering 4,000 units, and from July were turning out 9,000 units per month. Colt and Marlin-Rockwell Corp. also began production shortly after Winchester got into full production. Marlin-Rockwell, burdened by
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