Talk:Robinson Armament XCR

There has been a lot of back and forth in this article regarding the operating system of the XCR. Specifically, some argue that it is of the short-stroke type, and some that it is of the long-stroke type. In my last edit, I reverted a change so that the article (which now reads short-stroke) would be in agreement with the article on gas operation (http://en.wikipedia.org/wiki/Gas_operated). Apparently, to some this is unsatisfactory.

I propose that the references to stroke, either short or long be removed from this article until a source can be provided to show that one or the other view is correct. Once everyone is satisfied with the reference, then we may edit this and other related articles to reflect what we've learned.

The discussion seems to be one of semantics. The Gas Operated article refers to a long stroke as one where the piston moves under pressure for a distance greater than it's diameter. Short-stroke is where the piston moves under pressure for a distance less than it's diameter. The key words are under pressure. The distinction is made between a long and slow gas impulse that moves the parts the length of the weapon's operation and a sharp and fast gas impulse that imparts momentum to the piston and operating group of the weapon and is afterward vented. This definition, if true, means that the XCR (and pretty much every other modern gas-op firearm) uses the short-stroke operation. It can be summed up by saying that the stroke refers to the length of time that gas pressure impinges on the piston. The gas is what's doing the stroking, not the piston.

The other view is that the term stroke is entirely independent of how long gas impinges on the piston, and refers only to how far the piston moves: either longer or shorter than it's diameter. This definition would have the AK-47, the XCR, and any other weapon where the piston moves the same distance as the rest of the operating group as a long-stroke operation. I believe this is the common usage of the term as applies to engines. The difference is that in engines the diameter of a piston contributes an effect on the operation of the engine, but in firearms the diameter of a piston contributes nothing to the operation (and probably only affects the rigidity and weight of the piston itself, and the effect that that has on felt recoil). In this definition, it's the piston doing the stroking, not the gas.

I'll see if this generates any discussion and make the change to stroke free in a couple of days if we haven't got it resolved by then. CrunchRiff (talk) 06:26, 6 July 2008 (UTC)