Direct impingement

Direct impingement
direct impingement

Direct impingement is a type of gas operation for a firearm that directs gas from a fired cartridge directly to the bolt carrier or slide assembly to cycle the action.

Contents

Evaluation

Unlike conventional gas-operated firearms, direct impingement does away with a separate gas cylinder, piston, and operating rod assembly. High-pressure gas acts directly upon the bolt and carrier thereby saving weight, lowering costs, and reducing the mass of the operating parts.

The main disadvantage of direct impingement is that the breech of the firearm becomes fouled more quickly. This is caused by solids from the high-temperature gas condensing on the bolt face and primary operating mechanism. The combustion gases contain vaporized metals, carbon, and impurities in a gaseous state until they contact cooler operating parts. The deposits increase friction on the bolt's camming system leading to jams, so that thorough and frequent cleaning is required to ensure reliability. The amount of fouling depends upon the rifle's design as well as the type of propellant powder used. For example, the French MAS 44 and MAS 49 series of rifles was known to have been successfully operated for years with corrosive-primed ammunition using ordinary field cleaning expedients such as gasoline (as solvent) and straight-grade motor oil (as lubricant).[citation needed] While the 7.62mm Armalite AR-10 proved fairly resistant to malfunctions caused by deposit fouling, the smaller 5.56mm M16A1 experienced significantly increased malfunctions due to fouling and carbon deposits after a change in propellant specifications.

A further disadvantage of direct impingement is that combustion gases heat the bolt and bolt carrier as the firearm operates. This heating may alter the temper of metal parts, accelerating wear and decreasing the service life of the bolt, extractor, and extractor spring. Heat dries up lubricant and makes the operating parts difficult to handle when clearing malfunctions. Heat can also melt the lacquer coatings of steel cartridge cases, gumming up parts. Thermal expansion in the action can result in loss of tolerances and consequent degradation in accuracy.

Conversely, in a conventional gas piston design such as the Armalite AR-18, gas used to operate the firearm is isolated from the breech and contained within the gas cylinder then vented away from other working parts. Some systems actually contain the gas completely and vent excess back into the barrel, such as the M1 Carbine and FN SCAR.

History

The first experimental rifle using a direct impingement system was the French ENT 1901 Rossignol B1 rifle followed by Rossignol's B2, B4 and B5. The first successful production weapon was the MAS 40 rifle adopted in March 1940. The Swedish Ag m/42 is another well-known example. Both the French and Swedish rifles use a simple system whereby the gas tube acts as a piston with a cylinder recess in the bolt carrier.

The premier current example of direct impingement is the AR-15/M16 rifle designed by Eugene Stoner who first designed the Armalite AR-10. In the Stoner system covered by U.S. Patent 2,951,424, gas is routed from a port in the barrel directly to a chamber formed in the bolt carrier. The bolt acts as the piston and is sealed with small automobile-style piston rings.

See also

Bibliography

  • Centre des archives de l'armement, Châtellerault. National Armament Archives Center.
  • Huon, Jean. Proud Promise—French Semiautomatic Rifles: 1898-1979, Collector Grade Publications,1995,ISBN 0-88935-186-4

References


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • M16 rifle — Rifle, 5.56 mm, M16 From top to bottom: M16A1, M16A2, M4A1, M16A4 Type Assault rifle Place  …   Wikipedia

  • M4 carbine — M4A1 redirects here. For the World War II tank, see M4 Sherman. For the World War II rifle, see M4 Survival Rifle. Carbine, 5.56 mm, M4 An M4 with an aftermarket buttstock, Rail Adapter System (RAS), fl …   Wikipedia

  • AR-15 — The AR 15 comes in many sizes and has many options, depending on the manufacturer. The part shown bottom center is the lower receiver, which under US law is the component legally considered the firearm . Type …   Wikipedia

  • Comparison of the AK-47 and M16 — M16 (top) and AK 47 (bottom) assault rifles Firearm AK 47 M16A1 Manufacturer Izhmash ArmaLite, Colt …   Wikipedia

  • Firearm action — In firearms terminology, an action is the system of operation used to load rounds and/or seal the breech. In many weapons a breechblock reciprocates in the receiver of the firearm. The term is also used for the physical parts inside the weapon… …   Wikipedia

  • MAS-49 rifle — Infobox Weapon name= MAS 49 caption= origin= flagcountry|France type= Semi automatic rifle is ranged=yes is UK= service=1951 1979 used by=France, Syria wars= First Indochina War, Algerian War of Independence, Suez Crisis, Vietnam War designer=… …   Wikipedia

  • Eugene Stoner — Eugene Morrison Stoner (Born November 22, 1922 in Gosport, Indiana; died death date and age|1997|4|24|1922|11|22 in Palm City, Florida) is the man most associated with the design of the AR 15, which was adopted by the military as the M16. He is… …   Wikipedia

  • Rasheed Carbine — Infobox Weapon|is ranged=yes caption=Top to bottom: Swedish AG 42B Ljungman rifle, Egyptian Hakim rifle, Egyptian Rasheed carbine name=Rasheed Carbine type=Semi automatic carbine origin=Egypt (designed in Sweden) era=Modern design date= prod… …   Wikipedia

  • Gas-operated reloading — Gas operation is a system of operation used to provide energy to operate autoloading firearms. In gas operation, a portion of high pressure gas from the cartridge being fired is used to power a mechanism to extract the spent case and chamber a… …   Wikipedia

  • SR-47 — Infobox Weapon|is ranged=yes name=SR 47 caption=SR 47 assault riffle origin=flagcountry|United States type=Assault rifle designer=Knight Armament Co. design date= service=Never entered into service cartridge=7.62x39mm action=direct impingement… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”