The Beardmore-Farquhar machine gun was one of the lightest machine guns ever constructed, weighing only 16*4 pounds with a 77-shot drum magazine attached and loaded with the .303 British service cartridge. This weapon was the invention of Col. Moubray Gore Far-quhar, of Birmingham, England, and was manufactured by Messrs. William Beardmore & Co., also located in Birmingham.
Many special features were claimed by the promoters, such as its cheapness to manufacture, the practically jam-proof mechanism, perfect breech locking and a safety feature making it impossible to fire the weapon without the breech being securely locked. It was recommended that no oil be used on the highly polished close-fitting mechanism, thus making it an ideal weapon for an observer in a plane where great altitude gummed up the working parts of similar firing mechanisms that demanded lubrication. The makers of the gun also claimed the heat of the barrel did not affect the other parts, as they would continue to function properly even if the barrel was red hot during the entire time of opera t ion.
The weapon was similar in appearance to other drum fed observer guns that had been used so surecssfullv bv the British Royal Air Force tt /
during World War 1. The manufacturers, however, considered it to be a real improvement over similarly constructed ones because of its unusual
method of operation.
The most unique feature of the gun is the extensive use of springs for its operating energy. It is placed in the unusual classification of being actuated by both gas piston and spring. The power of the exploding powder charge does not act directly on the bolt's unlocking mechanism but compresses and stores up spring energy until the bore pressure chops to a safe operating limit. The bolt is then unlocked by the smooth action of the strong spring, which gives positive unlock ing without the jarring effect of a straight gas-piston-driven mechanism. The piston is contained in a cylinder which is fastened to the barrel and connected to the bore by a drilled orifice. The main driving spring is housed in the front end of a part known as the spring tube, with a kind of sear device also located in this part. The front of the housing is held in position by a tube cap and fore end piece.
The design of this peculiar weapon also has what is called the bolt-closing spring. It is placed around a central rod, and when installed, is located at the rear of the spring tube underneath the barrel.
When the cartridge is fired and the bullet passes the orifice in the barrel, gas is bled into t he gas-cylinder chamber forcing the piston rearward and compressing the main spring until it is held in this position by the catch or sear. The spring is thus compressed between the catch and head of the tube. It remains compressed until the resistance to turning the bolt head, caused by the pressure of the gas in the chamber working on the locking lugs against the body, is so reduced that it can be overcome by the strength of the compressed spring.
The main spring held securely by the scar, with its firm abutment against the holding washer, extends rearwards carrying with it the bolt canier to which the bolt is attached. The force of the main spring, upon opening the bolt, extracts and ejects the empty cartridge case and compresses the bolt-closing spring. The main spring, now being fully extended and no longer pressing against the sear and catch, disengages, allowing the now-compressed bolt-closing spring to start, counterrecoil movement of the parts. They in turn strip a fresh round from the feeder and return the main-spring-sear washer and piston to battery position and in the final movement forward lock the bolt securely to the barrel.
The breech action is of the straight-pull type
3eardmcre-f,firquhar A)icra:t Machine Gun, Cal. .303
whereby the boh carrier slides in slots outside
the body. The carrier is provided with an internal cam slot which engages the bolt arm. The
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