page_title: Gas-operated reloading
section_title: Long-stroke piston
hierarchical_section_title: Gas-operated reloading / Gas systems / Long-stroke piston
caption_attribution_description: English: long stroke gas piston Zeos386sx (talk) 01:24, 13 February 2011 (UTC)
context_page_description: Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent case and insert a new cartridge into the chamber. Energy from the gas is harnessed through either a port in the barrel or a trap at the muzzle. This high-pressure gas impinges on a surface such as a piston head to provide motion for unlocking of the action, extraction of the spent case, ejection, cocking of the hammer or striker, chambering of a fresh cartridge, and locking of the action.
context_section_description: With a long-stroke system, the piston is mechanically fixed to the bolt group and moves through the entire operating cycle.  This system is used in weapons such as the Bren light machine gun, AK-47, Tavor, FN Minimi, M249 Squad Automatic Weapon, FN MAG, FN FNC, and M1 Garand. 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. The primary disadvantage to this system is the disruption of the point of aim due to several factors such as: the center of mass changing during the action cycle, abrupt stops at the beginning and end of bolt carrier travel, and the use of the barrel as a fulcrum to drive the bolt back. Also, due to the greater mass of moving parts, more gas is required to operate the system that, in turn, requires larger operating parts.
caption: Long stroke gas piston, from an AK-74.
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