M1919 Browning machine gun The M1919 Browning is a . 30 caliber medium machine gun widely used during the 20th century , especially during World War II , the Korean War , and the Vietnam War . An air - cooled development of the standard US machine gun of World War I , the John M . Browning - designed M1917 , the M1919 saw service as a light infantry , coaxial , mounted , aircraft , and anti - aircraft machine gun by the U . S . and many other countries . Although it began to be superseded by newer designs , such as the M60 , in the later half of the century , it remained in use in many North Atlantic Treaty Organization ( NATO ) countries and elsewhere for much longer . The M1919 is very similar in design to the larger Browning - designed . 50 caliber ( 12 . 7mm ) M2 Machine Gun , especially in its " heavy - barrel " or HB version , still in NATO service . Many M1919s were rechambered for the new 7 . 62×51mm NATO round and served into the 1990s , as well as up to the present day in some countries . The United States Navy also converted many to 7 . 62mm NATO , and designated them Mk 21 Mod 0 ; they were commonly used on river craft in the 1960s and 1970s in Vietnam . Operation . Loading . The M1919 originally fired the . 30 cal M1906 ( 30 - 06 ) ball cartridge , and later the . 30 caliber M2 ball cartridge , contained in a woven cloth belt , feeding from left to right . A metal M1 link was later adopted , forming a " disintegrating " belt . Loading was accomplished by inserting the pull tab on the ammunition belt from the left side of the gun - either metal links or metal tab on cloth belts - until the belt - holding pawl at the entrance of the feed way grabbed the belt and held it in place . The cocking handle was then pulled back with the palm of the hand facing up , and then released . This advanced the first round of the belt in front of the bolt for the extractor / ejector on the bolt to grab the first cartridge . The cocking handle was pulled and released a second time . This removed the first cartridge from the belt , advanced the next round into position to be grabbed and moved the first round down into the chamber of the barrel ready for firing . As the bolt went into battery , the extractor grabbed the next round on the belt that was advanced and was resting in the feedway waiting to be loaded . Every time the gun fired a single shot , the gun performed the sequence of extracting and ejecting the spent round as the bolt came rearward , loading the next round to be fired into the barrel , advancing the belt , grabbing the next round in preparation for loading , then chambering it as the bolt came forward again under tension from the spring . If the trigger was held down , the gun would continue to fire in full automatic , repeating the sequence over and over until stopped . The gun ' s original design was as a water - cooled machine gun ( see the M1917 Browning machine gun ) . When it was decided to try to lighten the gun and make it air - cooled , its design as a gun that fires from the closed bolt created a potentially dangerous situation . If the gun was very hot from prolonged firing , the cartridge ready to be fired could be resting in a red hot barrel , causing the propellant in the cartridge to heat up to the point that it would ignite on its own without warning . With each further shot heating the barrel even more as this happened , the gun would continue to fire and become uncontrollable until the ammunition ran out , since the trigger was not what was causing the gun to fire in this situation . This is known as a cook - off , and was the reason gunners were taught to cock the gun with the palm facing up , so that in the event of a cook - off , their thumb wouldn ' t be dislocated by the reciprocating charge handle . Gunners were trained to manage the barrel heat by firing in controlled bursts of three to five rounds , with a delay between bursts to delay its heating . Most other machine gun designs would be fired in the same way , even though most feature quick change barrels and fire from an open bolt , two features that make air - cooled machine guns capable of sustained fire , and features that the M1919 design lacked . Firing . When the gun was ready to fire , a round would be in the chamber and the bolt and barrel group would be locked together , with the locking block at the rear of the bolt . When the rear of the trigger was pivoted upwards by the operator , the front of the trigger tipped downward , pulling the sear out of engagement with the spring - loaded firing pin , allowing it to move forward and strike the primer of the cartridge . As the assembly of bolt , barrel and barrel extension recoiled to the rear of the gun upon firing , the locking block was drawn out of engagement by a cam in the bottom of the gun ' s receiver . The recoiling barrel extension struck the " accelerator " assembly , a half - moon shaped spring - loaded piece of metal pivoting from the receiver below the bolt and behind the barrel extension . The tips of the accelerator ' s two curving fingers engaged the bottom of the bolt and caused it to move rapidly to the rear . The extractor - ejector was a mechanism that pivoted over the front of the bolt , with a claw that gripped the base of the next round in the belt . A camming track in the left side of the receiver caused this to move down as the bolt moved back , lowering the next round down on top of the fired case , pushing it straight down out of the extraction grooves of the bolt face through the ejection port . A spring in the feed tray cover pushed the extractor - ejector down onto the next round , so if the feed tray cover was opened , the extractor - ejector would be pulled upwards if the belt needed to be removed . The belt feed lever was connected to the belt feeding pawl at the front end , had a cam pin at the rear end which ran through a track in the top of the bolt , and a pin in the feed tray cover acted as the pivot between the two ends . The rearward movement of the bolt caused the rear end of the feed lever to pull to the right , causing the feeding pawl at the other end to move left over the belt . The pawl would pull the belt further to the right as the bolt came forward again , also sending the loose M1 link of the previous round to be taken out of the belt to fly out the right side of the receiver . A recoil buffer tube extended from the back of the receiver to make the cycle of the bolt smoother than previous designs , to absorb some of the recoil of the bolt , and formed a place for the pistol grip to be installed . Except for the M1919A6 , all other variants had to be mounted on a tripod or other type of mount to be used effectively . The tripod used by infantry allowed traverse and elevation . To aim the gun along its vertical axis , the adjustment screw needed to be operated . This allowed the gun to be pointed upwards or downwards , with free traverse to either side . The gun was aimed using iron sights , a small folding post at the front end of the receiver and a rear aperture sight on a sliding leaf with range graduations from 200 to 1 , 800 meters in 200 meter increments . When folded down , the aperture formed a notch that could be used to fire the gun immediately without flipping up the leaf . The rear sight also had windage adjustment with a dial on the right side . Operational use . Infantry . As a company or battalion support weapon , the M1919 required at least a two - man machine gun team . But , in practice , four men were normally involved : the gunner ( who fired the gun and when advancing carried the tripod and box of ammo ) , the assistant gunner ( who helped feed the gun and carried the gun , and box of spare parts and tools ) , and two ammunition carriers . The original idea was to allow the gun to be more easily packed for transport , and featured a light barrel and bipod when first introduced as the M1919A1 . Unfortunately , it quickly became clear that the gun was too heavy to be easily moved , while at the same time too light for sustained fire . This led to the M1919A2 , which included a heavier barrel and tripod , and could be continuously fired for longer durations . The M1919A4 weighed about , and was ordinarily mounted on a lightweight , low - slung tripod for infantry use . Fixed vehicle mounts were also employed . It saw wide use in World War II mounted on jeep s , armored personnel carriers , tank s , and amphibious vehicles . The M1919A4 played a key role in the firepower of the World War II US Army . Each infantry company normally had a weapons platoon in addition to its other organic units . The presence of M1919A4 weapons in the weapons platoon gave company commanders additional automatic fire support at the company level , whether in the assault or on defense . The A5 was an adaptation of the A4 with a forward mounting point to allow it to be mounted in tanks and armored car s . This , along with the M37 and the Browning M2 machine gun , was the most common secondary armament during World War II for the Allies . Another version of the M1919A4 , the M1919A6 , was an attempt to make the weapon into a light machine gun by attaching a buttstock and lighter barrel — 4 lb ( 1 . 8 kg ) instead of 7 lb ( 3 . 2 kg ) . The A6 version was in fact heavier than the A4 without its tripod , at 32 lb ( 15 kg ) , though its bipod made for faster deployment and enabled the machine gun team to dispense with one man ( the tripod bearer ) . The A6 version saw increasing service in the latter days of World War II and was used extensively in Korea . The A6 variant had a folding bipod mounted on the front of the gun , a sheet - metal buttstock , carrying handle , and a tapered barrel . While the modifications were intended to make the weapon more useful as a squad light machine gun , it was a stopgap solution , as the M1919A6 was heavier than the old Lewis gun of World War I , let alone the contemporary light machine guns of other nations . The M1919A6 was an attempt to combine the portability and low profile of the M1918 BAR with the sustained firing capability of the M1919A4 . The M1919A4 was given a lighter barrel , buttstock , pistol grip , carrying handle , flash suppressor , and bipod to achieve the conversion . Even though it was reliable , it proved impractical for combat . While the M1919A4 had a crew of two or more to carry the gun and the tripod , one M1919A6 gunner was expected to carry and deploy the gun by himself . During the Second World War , two additional variants of the M1919 were adopted by the US military . One version was the coaxial M37 variant , with the ability to feed from either the left or the right of the weapon . The M37 also featured an extended charging handle similar to those on the M1919A4E1 and A5 . A trial variant fitted with special sighting equipment was designated M37F . In the late 1950s , a M1919 designed for remote firing via a solenoid trigger was developed for use in the XM1 / E1 armament subsystem was designated M37C . The US Navy later converted a number of M1919A4s to 7 . 62mm NATO chambering and designated them Mk 21 Mod 0 ; some of these weapons were employed in Vietnam in riverine warfare patrols . From the 1960s until the 1990s , the Israel Defense Forces ( IDF ) used ground tripod and vehicle - mounted M1919A4 guns converted to 7 . 62mm NATO on many of their armored vehicles and M3 personnel carriers . Israel developed a modified link for these guns due to feeding problems with the original US M1 link design . The improved Israeli link worked with . 30 caliber , 7 . 62mm NATO and 8×57mm cartridges . Aircraft . With assistance from firearms engineers at Fabrique Nationale de Herstal , Belgium , the Model 1919 was completely re - engineered into the . 30 caliber M2 AN ( Army - Navy ) aircraft machine gun ( see # AN / M2 ) . The . 30 in M2 AN Browning was widely adopted as both a fixed ( offensive ) and flexible ( defensive ) weapon on aircraft . Aircraft machine guns required light weight , firepower , and reliability , and achieving all three goals proved a difficult challenge , with the mandate for a closed bolt firing cycle to enable the gun to be safely and properly synchronized for fixed - mount , forward - aimed guns firing through a spinning propeller , a necessity on many single - engined fighter aircraft designs through to nearly the end of World War II . The receiver walls and operating components of the M2 were made thinner and lighter , and with air cooling provided by the speed of the aircraft , designers were able to reduce the barrel ' s weight and profile . As a result , the M2 weighed two - thirds that of the 1919A4 , and the lightened mechanism gave it a rate of fire approaching 1 , 200 rpm ( some variants could achieve 1 , 500 rpm ) , a necessity for engaging fast - moving aircraft . The M2 ' s feed mechanism had to lift its own loaded belt out of the ammunition box and feed it into the gun , equivalent to a weight of 11 lb ( 5 kg ) . In Ordnance circles , the . 30 M2 AN Browning had the reputation of being the most difficult - to - repair weapon in the entire US small arms inventory . The M2 also appeared in a twin - mount version which paired two M2 guns with opposing feed chutes in one unit for operation by a single gunner , with a combined rate of fire of 2 , 400 rpm . All of the various M2 models saw service in the early stages of World War II , but were phased out beginning in 1943 , as hand - trained defensive machine guns became obsolete for air warfare ( the . 50 in / 12 . 7 mm M2 Browning and 20 mm automatic cannon had replaced the . 30 in as offensive air armament as well ) . The . 30 in M2 aircraft gun was widely distributed to other US allies during and after World War II , and in British and Commonwealth service saw limited use as a vehicle - mounted anti - aircraft or anti - personnel machine gun . Other calibers . The same basic weapon was also chambered for the British . 303 round , and was used as a basic fighter aircraft gun in fighters such as the Supermarine Spitfire until the widespread introduction of the larger caliber Hispano - Suiza HS . 404 cannon , and throughout the war in bombers — British night fighters like the Mosquito and Beaufighter used quartets of . 303 Brownings in the nose , with four 20mm Hispano cannon in ventral fuselage mounts . Similar versions for a variety of European calibers were delivered by the Belgian gun maker FN ( Fabrique Nationale ) , notably German - standard 7 . 92×57mm Mauser which was widely used in Eastern Europe ; and by Swedish gun maker Carl Gustaf SGF in 6 . 5×55mm and 8×63mm calibers . Argentina used Colt - manufactured guns chambered for the standard Argentine 7 . 65×53mm cartridge . US - manufactured M1919s were converted to the 7 . 62×54mmR cartridge by both the People ' s Republic of China and North Vietnam in order to use captured guns with their standard machine gun ammunition . The standard links and belts for the M1919 were retained . Similar conversions are available on the US commercial market for recreational shooters to take advantage of cheap surplus 7 . 62×54mmR ammunition . On Soviet aircraft . The . 303 variant equipped the Hawker Hurricane s delivered to Soviet Air Force s , during the Great Patriotic War . Soviet airmen compared them to Soviet ShKAS in terms of reliability : " But they often failed due to dust , " recalled pilot Nikolai G . Golodnikov . " We tackled the problem gluing percale on all the machine - gun holes , and when you opened fire , bullets went right through . The machine guns became reliable then . They were of low efficiency when fired from distances of 150 - 300m . " Production . The M1919 was manufactured during World War II by many different companies in the USA , including the Saginaw Steering Gear division of the General Motors Corporation , Buffalo Arms Corporation , and Rock Island Arsenal . In the UK , production was chiefly by BSA . Originally unit priced at $ 667 each , mass production lowered the price to $ 141 . 44 . Variants and derivatives . M1919 variants . In total there were six variants of the basic M1919 machine gun . < br > The original M1919 was designed to use in tanks . It featured a relatively heavy barrel , attempting to match the sustained fire capability of contemporary water - cooled machine guns . < br > The M1919A1 featured a lighter barrel and a bipod . < br > The M1919A2 was another lightweight development specifically for mounted cavalry units , utilizing a shorter barrel and a special tripod ( though it could be fitted to either the M1917 or M2 tripods ) . This weapon was designed to allow greater mobility to cavalry units over the existing M1917 machine gun . The M1919A2 was used for a short period between World War I and World War II after the cavalry had converted from horses to wheeled and tracked vehicles . < br > The M1919A3 , an improved version of the M1919A2 , was also developed . M1919A4 . However , by and large the most common variant of the series was the M1919A4 . The M1919A4 was used in both fixed and flexible mounts , by infantry and on vehicles . It was also widely exported after World War II and continues to be used in small numbers around the world . Two variants were developed specifically for vehicular use , the M1919A5 , with an extended charging handle , and the M1919A4E1 , a sub - variant of the M1919A4 refitted with an extended charging handle . M1919A6 . The M1919A6 was an attempt to provide US forces with a more portable light machine gun , similar to the German MG 34 and MG 42 machine guns that they were facing . The M1919A6 had a metal buttstock assembly that clamped to the backplate of the gun , and a front barrel bearing that incorporated both a muzzle booster and a bipod similar to that used on the M1918 Browning Automatic Rifle ( BAR ) . A lighter barrel than that of the M1919A4 was fitted . The M1919A6 was a heavy ( ) and awkward weapon in comparison with the MG34 and MG42 and was eventually replaced in US service by the M60 machine gun in the 1960s . T66 Machinegun . The M1919A6 was used by Springfield Armory in the late 1940s and early 1950s as a testbed for an interim general purpose machinegun . It was rechambered for the experimental T65 series cartridges , culminating in 1951 with the T66 Machinegun chambered for the T65E3 cartridge ( one of the forerunners to the 7 . 62mm NATO cartridge ) . It had a new barrel with a flash - hider attachment , a shorter action , and modified M1 disintegrating belt links to feed the new cartridge . It was deemed still too heavy for field use and was not adopted . AN / M2 . A specific aircraft version of the . 30 caliber Model 1919A4 was manufactured by Browning as the . 30 AN / M2 . It had a thinner barrel and receiver walls to keep down weight . It was used on US aircraft early in World War II but the lighter . 30 - caliber weapon was increasingly relegated to training duties as the war progressed . A derivative of this weapon was built by Colt as the civilian market MG40 . It was later replaced by the larger caliber — and is not to be confused with — the Browning Machine Gun , Cal . . 50 , M2 , Aircraft , with the smaller calibre ordance bearing the official designation of " Browning Machine Gun , Cal . . 30 , M2 , Aircraft . " The . 50 AN / M2 " light barrel " version , used in the majority of fixed and flexible / turreted mounts on U . S . World War II - era aircraft as the war progressed , lacked the massive " cooling collar " of the heavy barrel M2HB version , which is still in service with the ground forces of the U . S . military in the 21st century . Browning . 303 Mark II . The Browning was adopted by the Royal Air Force as a replacement for the . 303 Vickers and manufactured by Vickers Armstrong and BSA to fire the . 303 round and named Browning . 303 Mk II in British Service . It was essentially the 1930 Pattern belt - fed Colt – Browning machine gun with a few minor modifications for British use , such as firing from an open bolt , hence prohibiting their use for gun synchronization through a spinning propeller . It was designed to fire hydraulically as a wing mounted machine gun but was also adopted as hand - fired mount for use in bombers and reconnaissance aircraft . It had a rate of fire of 1150 rounds per minute . The Browning . 303 was used on the RAF ' s ' eight - gun fighters ' the Hawker Hurricane and Supermarine Spitfire , and as a turret gun in the Boulton Paul Defiant , and in the Handley Page Halifax , Short Stirling , Avro Manchester and Avro Lancaster bombers , and the Short Sunderland flying boat installed in various Boulton Paul or Nash & Thomson turrets . For hand - held moveable mount use the Vickers K gun was preferred . T33 . The AN / M2 was on occasion used as an infantry gun . Called the T33 it was fitted with a buttstock and bipod to allow for use without a tripod or other mount . The T33 consists of a butt stock from a M1919A6 and a rear sight and bipod from a BAR 1918 . These conversions were based on field conversions carried out by soldiers in the Pacific Theater during World War II . A personally modified weapon of this type , using the butt stock from an M1 rifle , was used by Marine Corporal Tony Stein during the invasion of Iwo Jima . Stein would posthumously receive the Medal of Honor for his actions during the battle . It had a rate of fire in excess of 1 , 200 rpm and was nicknamed the " Stinger . " Barrel overheating and lack of control were the cause of its demise . M37 . In the late 1940s and early 1950s the US military was looking for an upgrade to the M1919 that could feed from either side for use as an improved coaxial machinegun . Saco - Lowell developed a model that had the driving spring attached to the back plate ( eliminating the need for a mainspring and driving rod protruding out the back of the bolt ) , a solenoid trigger for remote firing , a feed cover that could open from either side , a bolt with dual tracks that could feed from either side , and a reversible belt feed pawl , ejector , and feed chute . The experimental T151 had a flat backplate ( ? ) , the T152 had spade grips and a " butterfly " trigger like the M2HB , and the T153 had a pistol grip and back - up trigger like the M1919A4 and an extended charging handle similar to those on the M1919A5 . The T153 was adopted as the M37 and was produced by SACO - Lowell and Rock Island Arsenal from 1955 to 1957 . It was in regular service from 1955 until it was replaced by the M37E1 in the late 1960s and the M73A1 in the early 1970s . The M37 was used mostly on the M48 and M60 Patton medium tanks . The M37F was a trial variant fitted with special sighting equipment . The M37C was a variant without a sight bracket designed for use in aircraft armament ( like the skid - mounted XM1 / E1 helicopter armament subsystem ) . The M37E1 was a M37 machine gun converted by Rock Island Arsenal and Springfield Armory to chamber the 7 . 62×51mm NATO cartridge and feed the M13 disintegrating belt . They were designed for interim use until the M73 machine gun could be fielded . The M37E1 was to be standardized as the M37A1 but development of the improved M73A1 precluded this . Mk 21 Mod 0 . The increasing American involvement in Vietnam created a demand for small arms , especially the new M60 machinegun . The Navy had surplus machineguns left over from World War 2 and Korea , but they were chambered for the earlier . 30 - 06 Springfield cartridge rather than the new standard 7 . 62mm NATO cartridge . The Mk 21 Mod 0 was a US Navy conversion of the . 30 M1919A4 to fire the 7 . 62mm NATO cartridge . This was accomplished by replacing the barrel , bolt , and feed cover and adding a chamber bushing , a link - stripper , and a second belt - holding pawl to allow it to feed and fire the new cartridge . Spacer blocks were added to the front and back of the feedway to guide the shorter round and block the use of the longer . 30 - 06 Springfield ammunition . A six - inch flash hider was also added to the barrel to reduce the muzzle flash from firing the shorter cartridge . The conversions were performed from 1966 through 1967 at Naval Ordnance Station Louisville . Modified M1919A4s had the designation " " Machine Gun , 7 . 62mm / Mk 21 Mod 0 " " stamped on the receiver sideplate in 1 / 4 - inch lettering . The replacement barrels had " " 7 . 62mm NATO - G " " stamped on them in 1 / 8 - inch letters to differentiate them from M1919A4 or M60 barrels ; the letter " G " indicated it used a grooved barrel bushing . It used the standard 7 . 62mm NATO M13 link " strip - out " disintegrating link , in which the bolt pushes the round out of the bottom of the two - part link and then forwards into the breech . The old M1 link " pull - out " disintegrating links , which are pulled backwards out of the one - piece link by the extractor towards the bolt and then forwards into the breech , wouldn ' t feed through the new mechanism . The M1 links , which were designed for the longer and thinner . 30 - 06 Springfield , would also be too narrow to fit the shorter and thicker 7 . 62mm NATO round . The US Navy , because of their narrower inventory of 7 . 62mm NATO ammunition , used linked belts of either 7 . 62mm M80 Ball or a 4 : 1 ratio mix of 7 . 62mm M80 Ball and 7 . 62mm M62 Tracer . The refurbished feed mechanism was left - hand feed only . It was different from the one in the M60 GPMG in that the open end of the belt had to be on top so it could be stripped out . To prepare the ammo , gunners had to take out both of the 100 - round belts from an M19A1 ammo can , had to link them both together , and then loaded the resultant 200 - round belt back into the M19A1 can upside - down so it would feed correctly . International variants and derivatives . The M1919 pattern has been used in countries all over the world in a variety of forms and under a number of different designations . Commercial variants and derivatives . Colt MG40 . Colt produced a derivative of the M2 aircraft machine gun , the Colt MG40 . It shipped in a variety of calibers , including the basic . 30 - 06 Springfield and popular 7mm Spanish Mauser , and was available in left - or right - hand feed . < br > The MG40 - 2 Light Aircraft Machine Gun could be used in flexible - ( pintle - mounted ) , fixed - ( wing - mounted ) , or synchronized - ( through the propeller ) models . The Flexible mount machinegun came with grips and a " butterfly " trigger plate like the standard ground model . The Fixed model had a backplate . It used a cable connected to an operating slide connected to a stud on the bolt to fire it ; tension in the cable causes the trigger to activate and slack in the cable causes it to stop . The synchronized variant of the Fixed model had a trigger motor for through - propeller , gun synchronizing needs . Civilian ownership . The Browning M1919 remains popular with civilian enthusiasts in the United States , though changes in 1986 to the National Firearms Act of 1934 ( the US Federal law regulating private ownership of machine guns ) prohibited the registration of new machine guns for sales to private citizens , thus freezing the number of " transferable " machine guns in private ownership . The inflation of prices that followed , and the availability of parts from surplussed and scrapped machine guns , led to the development of semi - automatic versions of the Browning M1919 . Typically , these are built using a new right sideplate ( the portion legally considered the " firearm " under US law ) , which has a raised " island " protruding into the interior of the receiver . This requires the use of a modified bolt , barrel extension and lock frame which have been designed to allow only semi - automatic firing . The " island " prevents the insertion of unmodified full - automatic parts . A number of small gun companies have produced these " semi - auto machine guns " for commercial sales . The fairly simple modifications necessary to convert M1919 parts to the semi - automatic version , and the relatively easy process of riveting used in the assembly of the Browning machine gun ' s receiver , have also made it a popular gun for hobbyists to build at home . Similar " semi - auto machine guns " have been built using parts from other Browning pattern machine guns , to include the AN / M2 aircraft gun and FN30 , and variations that never saw military use such as extremely short ( 8 " ) barreled guns .