Talk:Direct impingement

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Direct Impingment refers to a gas system in which the gas from the bore acts directly on the piston face - with no expansion chamber. The FAL rifle and the AK-47 are classified by weapon engineers and professional armourers as Direct Impingment.

The Bleed-off and Expansion system used by the M16 family of weapons is ofetn refered to in marketing information as a Direct Gas system resulting in some confusion. The gas is allowed to expand in a pressure vessel that includes the gas tube and the expansion area in the bolt. Excess gas is then bled off through gas vents located on the side of the bolt carrier and also when the gas tube separates from the gas key.

By comparison an FN Minimi used an Expansion system due to the small cup on the piston that allows for some gas expansion where other long stroke pistons have no expansion space and are thus refered to as Direct Imopingement.

The M60 machine gun uses an Expansion and Cut-off system where the gas expands in the regulator and when the piston cup moves the gas hole is closed off cutting off the flow of gas.

I will post the text book references shortly.

Cheers,

Colt Armourer 00:57, 17 January 2007 (UTC)

You're incorrect. There is a piston face on EVERY gas operated firearm in existence. There is, by definition, also an expansion chamber. True, the FIRST Browning machinegun had a 'flapper'that utilized the expanding high-pressure gas after it exhausted into the air (as with the 'gas trap' variety of operating systems, but all of these are obsolete. This piston face can be in-line with the barrel as are the vast majority of them (the Colt Potato digger is an exception) but the BASIC operating principle of any gas operated weapon is that gas operates on a surface moving that surface.

Direct Impingement Means that this gas operates DIRECTLY on the bolt and bolt carrier rather than through a piston rod, extension, or other such mechanical connecting rod. The AK-47 is interesting in that the piston rod is a functional part of the bolt carrier being affixed albiet loosely sometimes. The FAL, however, is different in that the piston rod is not attached to the bolt carrier. There are variations... The HK G36 utilizes a conical surface with a 'nipple' in the middle. The Bang system utilizes a gas trap at the muzzle and a ring shaped 'piston'. There are many variations. The furthest from 'direct' one can cite is, I believe, the Colt Potato digger which utilizes a series of levers to operate the action. Not sure what armorers call such things... I'm a student of the gun, not a mechanic. --Asams10 05:11, 17 January 2007 (UTC)