Bolts - Piston vs Gas

[masterdrago]

I've got both gas ARs and a Sig 516 piston. I ran into some good deals on bolt pricing recently at RTB. I have the thought that all AR bolts are the same so will fit either a gas or piston carrier. Am I off the reservation or right on? I also read somewhere that a piston bolt has no need for gas rings since none hits the bolt innards but my OEM Sig bolt has them. Any thoughts?

[georgeib]

You're either going to need to call Sig to confirm, or try it yourself. Alternately, you can see if anyone on the Sig forums knows the answer.

FWIW, I know that a standard bolt, minus gas rings, will work in a PWS piston rifle.

[masterdrago]

FWIW, I bought a non Sig brand Carrier (LMT) and a M16 bolt Completion Kit from RTB w/gas rings. I got it a few days ago and assembled in the 516. I had gotten an email from LMT stating it was not designed for the Sig platform. I wanted a backup carrier. I was unable to purchase one from Sig CS, and LWRCI was out of stock. I fired yesterday using Hornady 75gr NATO ammo. At a gas block setting of .059" and suppressed it ejected in a nice pile at 3:00 about 8 feet out. At the .044" setting, the ejection was at 4:30, so slightly under gassed. The OEM BCG requires the .043 setting when suppressed with standard NATO 55gr ammo. I was using the OEM spring and buffer. Will check it with lighter ammo another time. So a non OEM bolt (gas) seems to work fine in my piston 516. I also got a good deal at PSA on a complete gas BCG so I have an extra for the gas gun and another bolt!