M1919 .30 Caliber Machine Gun
The M1919A4 .30 caliber machine gun is recoil operated, belt fed, and air cooled. In recoil operation the rearward force of the expanding powder gas furnishes the operating energy. The moving parts, while locked together at the moment of the explosion, are left free within the receiver to be forced to the rear by the recoil. This movement is controlled by means of various springs, cams, and levers, and is utilized to perform the necessary mechanical operations of unlocking the breech, extraction and ejection of the empty case, and feeding in of the new round, as well as cocking, locking, and firing the mechanism.
The M1919A4's receiver mechanism is for all practical purposes the receiver of the Browning machine gun, M1917. However, the weapon's rate of fire is also slower, at 400-550 rounds per minute.
The M1919A4 is provided with a heavy barrel that is exposed to the air. This factor serves to keep the gun at operating temperatures under normal conditions, i.e., at the rate of about 60 rounds per minute for about 30 minutes. Woven fabric belts of a capacity of 150 rounds, equipped with brass strips at each end to facilitate loading, as well as disintegrating metallic link belts could be used with the M1919A4 machine gun. When used as a ground light machine gun, the weapon is normally mounted on the M2 light machine gun tripod M2. In vehicle applications, the machine gun is mounted on various mounts, with an M2 tripod often provided to allow for the weapon to be dismounted.
The water-cooled Browning M1917 machine gun had entered limited service by the end of the First World War. The M1917 was used doctrinally as a heavy machine gun, with other weapons such as the Hotchkiss M1914 and Lewis M1917 machine guns providing lighter machine guns at lower echelons. The need for such weapons, and for a .30 caliber aircraft gun, led to the development of variants of the M1917 with heavy, air-cooled barrels. These were the M1918 aircraft machine gun and the M1919 ground machine gun. Adopted in 1918, the M1919 was so designated as to avoid confusion with the M1918 aircraft machine gun and the M1918 Browning Automatic Rifle.
The original M1919 machine gun was utilized as a fixed weapon for a variety of vehicle installations. Issues became apparent with both configurations. The M1919, essentially utilizing the barrel of the M1918 aircraft machine gun, was not capable of sustained automatic fire on the ground with no benefit of rushing cold air to cool it. The M1919 was originally provided in 2 configurations, one with no integral sights and one with a tubular sight unit. The latter was eventually redesignated as the M1919A1.
The Cavalry's interest in the weapon led to the development of flexible variants of the M1919 family. A 1917 requirement for a lightweight machine gun for Cavalry use had resulted in the development of a modified version of the M1918 Browning Automatic Rifle, the M1922. This was deemed unsatisfactory and a number of M1919s were acquired by the Cavalry branch, modified, and presented to the Ordnance Department as an alternative to the M1922. The result was the M1919A2. The M1919A2 featured a new rear sight and front sight attached to the barrel jacket to faciliate dismounted use. It also came with a new lightweight tripod. The end of horse cavalry in the US Army saw the M1919A2 utilized heavily in vehicular mountings. A variant with the front sight mounted on the front of the weapon's reciever, developed for the Infantry branch, was designated as the M1919A3.
The short 18 inch barrel was found to have determinental effects on the performance of then standard service ammunition in the 1930s. Variants of the M1919 and M1919A2 were subsequently tested by Rock Island Arsenal with 24 inch barrels. The differences between the two variants were largely limted to the fact that the variants of the M1919A2 used that sight configuration, while the variants of the M1919 used the M1919A3's sight configuration. The resulting weapon was designated as the M1919A4, the most common variant of the M1919 family. This weapon was used as both a company level flexible light machine gun on the M2 tripod mount and as a fixed machine gun on armored vehicles. It served in the United States military through the Second World War and afterwards and was widely exported.
The fixed machine gun variant was based on a variant that was developed for aicraft usage, which had supplanted the M1918 machine gun in that role. It differed only in the weapon's back plate, which lacked the pistol grip of the flexible variant. A solenoid was provided that allowed the weapon to be fired remotely. However, in many cases, new internal mounts lacked the requisite space to easily operate the weapon, and in some cases the wepaon could not even be easily mounted. A set of modifications were developed for the weapons, most visibly that of a bar allowing the weapon to be easily charged in confined spaces. The decision was eventually made to designate these weapons as M1919A5s. The new weapons included components from M1918 and M1919 aircraft guns. Similar conversions of basic M1919A4 machine guns were also done immediately following the Second World War, and were designated as M1919A4E1s.
Towards the end of the Second World War, the US Army again revisited developing a lighter, more maneuverable M1919 that could better support the infantry company in the assault and perhaps even be used as a substitute for the M1918 Browning Automatic Rifle. The resulting weapon, the M1919A6 .30 caliber machine gun was a belt-fed, air-cooled, recoil-operated machine gun that could be mounted on either a bipod or tripod mount. If necessary, the bipod legs could be folded to the rear, and the bipod rest legs used as a front support. The M1919A6 was similar to the M1919A4 except for a number of important differences. A removable metal shoulder stock was added and the barrel jacket was modified to mount a front barrel bearing and a removable bipod leg assembly with lock ring. A removable carry handle was added to the barrel jacket to allow easier handling of a hot weapon. The reciever cover latch was modified to provide easier opening. The driving spring was lightened to allow easier retracting of the bolt.
The weapon proved to still be too heavy and cumbersome for rapid changes of position. The weapon retained the ability to be used mounted on a tripod and was often employed this way as a substitute for the M1919A4. M1919A6s were also exported to US allies after the end of the Second World War.
With the introduction of the M60 7.62mm machine gun in the late 1950s, the M1919 family were phased out. The US Navy modified a number of M1919A4s to fire the new 7.62mm round and used these weapons, designated as Mk 21 Mod 0, through the conflict in Vietnam. A derivative of the M1919A4E1 and M1919A5 fixed machine guns was also developed after the end of the Second World War, designated as the M37, which was eventually replaced by the M73 machine gun.
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