In 1917, John Moses Browning was commissioned to create an automatic infantry firearm by the US military. The BAR was initially intended to be used by infantry during advance actions and fired from the shoulder or even from the hip. Automatic fire capabilities were supposed to allow suppression fire during the attack.
In 1918, the BAR was patented, tested, and launched into production, receiving M1918 designation in the US military. Early models had no bipods, nor support leg under the buttstock.
New guns were immediately field-tested on the Western Front during the First World War. Battle experience showed, that the BAR was too heavy (twice the weight of the M1 Garand), yet automatic fire off the shoulder or hip was hard to control due to the powerful .30-06 Springfield ammunition used.
However, the gun had proven to be robust enough otherwise, and had been reassigned to the role of support machinegun. In 1922, the BAR had been modified to be used as a machine gun, and the new modification had received the designation M1922. Modifications included bipod, support leg under the buttstock, finned barrel and different sights. These modifications had been specifically requested by the U.S. Cavalry.
Later in 1937, the BAR had been modified again - this time becoming M1918A1. This time, modifications had been geared towards cutting the cost and ergonomics. Barrel fins and the support leg under stock were removed, and stock shape had been changed for easier handling. Neither the M1922 nor the M1918A1 had been manufactured in large quantities.
In 1940, the BAR had been modified for the last time, becoming the M1918A2, which was the most popular model, staying in production from 1940s till mid-1950s. These modifications included more ergonomic changes, such as heat shield, carrying handle, return of buttstock support leg and new bipod placement. Also, in this modification, the BAR had no semi-automatic mode - instead it had high and low rates (650 RPM and 450 RPM, respectively).
Ever since the introduction of 7.62x51mm NATO, the BAR had been gradually pulled out of active service, and by 1960, was mostly retired. Attempts to redesign it to accept 7.62 NATO ammunition were unsuccessful.
The BAR is gas-operated, magazine-fed and air-cooled. It uses .30-06 Springfield ammunition (7.62x63mm), also found in the M1 Garand self-loading rifle, and the M1903 Springfield bolt action rifle. 20-round double-stacked magazines are used for feeding, and the barrel is fixed. Most versions of BAR have bipods; however, in the M1918A2 they were frequently removed as a weight saving measure.
Colt Monitor Automatic Machine Rifle (R 80)
This variant was a result of cutting costs. The barrel fins were removed, as well as the support leg on the buttstock. The stock shape was also changed from the M1922.
This variant was produced from the 1940s until the mid-1950s. A heat shield was added, along with a carrying handle and a bipod. The buttstock support leg was also re-added. There were two modes of fire; in reality, it simply slowed or sped up the cyclic rate (either 450 RPM or 650 RPM, respectively).
There is a new commercial Model 1918A3 BAR. It is a semi-automatic rifle. The action was redesigned to fire from a closed bolt and will not accept any GI automatic parts. Most of the rest of the weapon is USGI surplus parts. It is manufactured by Ohio Ordanence. The cost is between $2500–$3000 USD. It is chambered in 7.62x51mm NATO and .30-06 Springfield.
The HCAR is a modern M1918 with 30 round magazines and picatinny rails and lightened to 5.44kg.
Foreign and export variants
The BAR also found a ready market overseas and was widely exported. In 1919, the Colt's company developed and produced a commercial variant called the Automatic Machine Rifle Model 1919 (company designation: Model U), which has 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 handguard. These Colt automatic rifles were available in a number of calibers, including .30-06 Springfield (7.62x63mm), 7.65x53mm Belgian Mauser, 7x57mm Mauser, 6.5x55mm, 7.92x57mm Mauser and .303 British (7.7x56mmR). All of the 6.5x55mm-caliber Colt automatic rifles appear to have been sold directly to FN.
An improved version of the Model 1924, the Model 1925 (R75) would achieve 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: refer to US patents 1548709 and 1533968). The Model 1925 was produced in various calibers, including .30-06 Springfield (7.62x63mm), 7.65x53mm Belgian Mauser, 7x57mm Mauser, 7.92x57mm Mauser, and .303 British (7.7x56mmR) (no Colt-manufactured Model 1925 rifles in 6.5x55mm 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 1924 in small quantities for the Dutch Army). Between 1921 and 1928, FN Herstal imported over 800 Colt-manufactured examples of 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.
The Chinese Nationalist Army used the FN M1930 throughout the Second Sino-Japanese War. The Chinese BAR was chambered for the German 7.92x57mm 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 the war, small quantities of American equipment, including the BAR, made their way into mainland China.