You sir, have a problem. I know, that's not helpful.no51 wrote:So, I took my AR out to the range this weekend and experienced multiple failure to feeds. Maybe 8 or so rounds were semi-auto out of 60. It would not feed the next round reliably and it would not lock back on the last shot, narrowed it down to short stroking. Was running Federal .223 55gr FMJ (black box). I ruled out the magazine (had a Magpul 20rd, Bushmaster 20rd, and Promag 30rd), although it could be possible that I have 3 crappy mags.
I'd bet money it's not the bolt carrier that's causing the short stroking. The AR-15 was designed with the "full auto" carrier you're using; the semi-auto version was Colt trying to please the ATF years later.no51 wrote:I am using an M16 bolt carrier which is heavier than the AR BC which I think is causing this short stroking. The .223 ammo is too light to get it to cycle correctly. That or I somehow messed up the gas system. The front sight base doesn't seem to have any tell-tale leak marks. The gas rings on the bolt seem to be sealing. Could it be the gas tube?
I'd bet it's a gas problem. Which means it's either the tube or the front sight/gas block.
Looking at the tube, it looks a little off center to me. This can happen when you mount a barrel and it doesn't line up perfectly. An off center tube means there's resistance when the bolt carrier group slides into place, which could be causing your issues. Did you buy this AR new, or did you build it? How many rounds have you put through it? When was the last time you cleaned the gas tube?
Have you removed the handguards and checked to ensure the gas tube is firmly installed in the front sight base? Check to make sure the roll pin holding the tube in place is still there.
I don't think it's an ammo problem, and I'm pretty sure there's no such thing as a lighter buffer spring for an AR-15, and if there was, I would question the purpose of such a part.no51 wrote:I'm going to try out some NATO ammo if that will cycle, if not I'm thinking of getting a lighter main recoil spring.