Gas-operated reloading
The first mention of using a gas piston in a single-shot breech-loading rifle comes from 1856, by the German Edward Lindner who patented his invention in the United States and Britain.
[1] In 1866, Englishman William Curtis filed the first patent on a gas-operated repeating rifle but subsequently failed to develop that idea further.
[4] In 1887, an American inventor called Henry Pitcher patented a gas-operated conversion system that he claimed could be applied to any manually-operated magazine rifle.
[5] In 1890 he would patent and submit an original gas-operated rifle for testing by the US government but it performed poorly and was ultimately never adopted despite being offered commercially for the civilian market.
[7][8] In 1889, the Austro-Hungarian Adolf Odkolek von Újezd filed a patent for the first successful gas-operated machine gun.
Most gas-operated firearms rely on tuning the gas port size, mass of operating parts, and spring pressures to function.
The M14 rifle and M60 GPMG use the White expansion and cutoff system to stop (cut off) gas from entering the cylinder once the piston has traveled a short distance.
John Browning used gas trapped at the muzzle to operate a "flapper" in the earliest prototype gas-operated firearm described in U.S. patent 471,782 and used a slight variation of this design on the M1895 Colt–Browning machine gun "potato digger".
[citation needed] In the 1980s, Soviet designer Alexander Adov from TsKIB SOO modified the concept with a tube diverting gas from the muzzle to a standard long-stroke system (see below) in order to diminish influence of the gas engine on barrel and increase accuracy, but his sniper rifle wasn't adopted due to the dissolution of the Soviet Union.
[11] With a long-stroke system, the piston is mechanically fixed to the bolt group and moves through the entire operating cycle.
The primary advantage of the long-stroke system is that the mass of the piston rod adds to the momentum of the bolt carrier enabling more positive extraction, ejection, chambering, and locking.
It may directly push[12] the bolt group parts, as in the M1 carbine, or operate through a connecting rod or assembly, as in the Armalite AR-18 or the SKS.
This, in turn, enables better control of the weapon due to less mass needing to be stopped at either end of the bolt carrier travel and prevents hot combustion gases from being pushed into the internals and removes powder residue in the receiver which significantly improves reliability, increasing the lifespan of weapon parts by reducing instances of malfunctions under prolonged periods of extreme high rate of fire and suppressed shooting.
One principal advantage is that the moving parts are placed in-line with the bore axis meaning that sight picture is not disturbed as much.
[15] Direct impingement operation increases the amount of heat that is deposited in the receiver while firing, which can burn off and cover up lubricants.
