M1918 Browning Automatic Rifle - Variants and Subsequent Models

Variants and Subsequent Models

During its lengthy service life, the BAR underwent continuous development, receiving many improvements and modifications. The first major attempt at improving the M1918 resulted in the M1922 light machine gun, adopted by the United States Cavalry in 1922. 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 endplate, fixed to the stock retaining sleeve. The handguard was changed, and in 1926, the BAR's sights were redesigned to accommodate the heavy-bullet 172-grain M1 .30-06 ball ammunition then coming into service for machine gun use.

In 1931, the Colt Arms Co. introduced the Colt 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 Colt Monitor omitted the standard bipod, instead featuring a separate pistol grip and buttstock 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. empty, the Colt Monitor had a rate of fire of approximately 500 rpm. Around 125 Colt Monitor automatic machine rifles were produced; of these ninety were purchased by the FBI. Eleven rifles went to the U.S. Treasury Department in 1934, while the rest went to various state prisons, banks, security companies, and accredited police departments. Although the Colt Monitor was available for export sale, no examples appear to have been exported to other countries.

In 1932, a greatly shortened version of the M1918 BAR designed for 'bush warfare' was developed by USMC Major 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 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. and was only 34.5 inches (880 mm) long overall. Though it proved superior to the M1918 in accuracy when fired in automatic mode using the prone position, and equal in accuracy to the standard M1918 at ranges of 500-600 yards when fired from a rest, it 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-barrelled 'jungle' BARs for further evaluation, no further work 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 was commenced on an improved BAR for the U.S. Army. The latter 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 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.

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 was shelved in favor of a rate-reducer mechanism designed by Springfield Armory, and housed in the buttstock. 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 handguard 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 walnut buttstock is approximately one inch longer than the M1918 BAR buttstock. The M1918A2 barrel was also fitted with a new flash suppressor, and fully adjustable iron sights. Late in 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 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 168,000 new weapons were manufactured). In 1942, a shortage of black walnut for buttstocks and grips led to the development of a black plastic buttstock for the BAR. Composed of a mixture of Bakelite and Resinox, and impregnated with shredded fabric, the buttstocks were sandblasted to reduce glare. Firestone Rubber and Latex Products Company produced the plastic buttstock for the U.S. Army, which was formally adopted on March 21, 1942.

Production rates greatly increased in 1943 after IBM introduced a method of casting BAR receivers from a new type of malleable pig iron developed by the Saginaw division of General Motors, called ArmaSteel. After successfully passing 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 the Korean War, M1918A2 production was resumed, this time contracted to the Royal McBee Typewriter Co., which produced an additional 61,000 M1918A2s.