AR-15 short stroking?

[mtdawg169]

Hey guys, I've got a 14.5" carbine length AR here that is acting a little weird. When shooting factory PMC 55 gr or Winchester 45 gr frangible I think its short stroking, the round ejects but the next round gets jammed sideways when attempting to feed (I think the bolt carrier isn't going far enough backward). I confirmed this by loading a couple magazines with 1 round and firing, and it would not lock back. I then loaded some of my own reloaded 5.56 that are considerably hotter than factory .223 (but not maximum loads) and it locked back every time.

The weird thing is works fine for the first magazine full of PMC (so a clean rifle, or cold I guess). But then sometime after about 30 rounds it short strokes every shot. Any help? My full set up is:

14.5" spikes upper with carbine length gas system
Spikes BCG (full auto version)
Carbine buffer and spring

Thanks for any help!

Is this a new gun? Has it been lubed properly? How does it run on 5.56 ammo?

Check the gas rings on the bolt. It sounds to me like they may be lined up with each other. The gaps have to be offset.

Staggering of the gas rings is not necessary.

Might have to step up the gas port in barrel as u are using a full auto carrier that is heavier for a reduced rate of fire. Or a lighter buffer and spring setup. Similiar threads on ar15.com for short stroking also.

The carrier weight isn't that much different and changing gas port size is not an option for most. I'd send it back to the manufacturer before trying to drill out the port. Once you do, it's your problem, not the manufacturers. Finally, since you're already running a CAR buffer, there is no lighter option. Only option is to run better ammo. It's odd that a carbine gassed barrel is short stroking with a CAR buffer. They usually require an H2 or even H3 buffer. If it's new, hopefully a few hundred rounds of good ammo will break it in well enough that you can run anything you want in it later.