OK here it goes...I've built a fal, short gas system with 16" barrel. I'm having cycling trouble. I have drilled out the gas port to .125 and it has started to work but I wadded up a gas piston that I turned from stainless stock, not sure of the alloy, so I ordered a used metric one. Has any body done this. Did you shorten the return spring and how much. I am thinking of turning down the second guide on the gas piston to give the spring more room to avoid coil binding and then shorten the spring a little, say half as much as is cut off the gas piston............:hmmmm2: