Short stroking

[togor]

Well there are two different mechanisms in the M1 that sort of oppose each other, and either can cause a failure of a new round to be stripped when the bolt cycles--a malfunction commonly referred to as short stroking. True short stroking occurs if the gas system is weak and the main spring is strong (your initial condition, as I understand it). In that case you get a true short stroke, where the bolt doesn't travel back far enough to engage the head of the next round. In the other case, where the gas system is strong but the spring is weak, the bolt travels back far enough--perhaps even too hard--but the compressed spring does not have enough power to advance the rounds up in the en bloc quickly enough to cause the top round to be caught & stripped by the return stroke of the bolt.

There is spare capacity in both the gas system and the spring, and so to the extent to which they age together, the rifle can continue to function. This may explain why a USGI spring works when a new one does not, if that is your observation. The USGI specs on a piston diameter are .5252" to .526". Jim Swartz put a new piston on for me shortly before he gave up the trade. Interestingly enough this one measured about .5263". I don't believe he meant to make it oversize but at those dimensions some error is inevitable. That oversize makes this a good op-rod to mate with a worn gas cylinder.

[finloq]

Jim may have slowed down, but he did the piston on my HRA op rod last month. Received, worked on and shipped back to me the next day.