User talk:CrunchRiff

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The AK47 features a long stroke gas piston, attached to bolt carrier

Short stroke pistons are found in and used by the AR18, LWRC and HK416.

The XCR is a long stroke piston design. Not short stroke

Nope. Sorry, but this is a common misnconception. The stroke does not refer to how the op-rod/piston interfaces with the bolt/carrier. All of your above examples are short stroke systems.

Here's from the wiki article http://en.wikipedia.org/wiki/Gas-operated_reloading, which gets it right:

"A short-stroke gas system is defined as one that diverts high pressure gas from the middle or rear portion of the barrel that impinges on the piston head for a short period of time before excess gas is either cut-off (M14), vented (AK-47), or the piston head reaches a stop (M1 Carbine).[1] The distance the piston travels under pressure is generally less than its diameter.[2] The piston may or may not be attached to the bolt carrier. This is the most common type of gas operation.

A long-stroke gas system is generally defined as one which the stroke of the piston under pressure is greater than its diameter.[3] Because of the greater dwell time, gas must be ported from the barrel very near the muzzle of the weapon as in the M1 Garand. This relatively lower pressure gas acts over a longer period of time to impart the same amount of energy to the operating system. Because the operating parts are longer, they are necessarily heavier and this system is not used in modern weapons."

So, even if the piston is attached to be bolt/carrier,in a short-stroke system the gas only pushes it for a short while. Momentum carries it through the rest of its motion and cycles the weapon. CrunchRiff (talk) 12:36, 11 June 2008 (UTC)