re: Official AR-15 thread

Hey guys, I'm having a problem with my AR. I've tried several types of ammo and I cant get it to cycle right. I tried different mags too. I used Tula, Monarch, and Federal American Eagle. All 55gr FMJ. I thought it might be short stroking with the cheap ammo, but the bolt locks back with only one round in the mag. It had several issues the last time I used it, it would not pick up the next round, and it tried to load two rounds sideways it looked like. The tip of the bullet missed the chamber and the bcg struck the side of the casing jamming it. Do ya'll have any idea on where I should start with trying to fix this. I picked this gun up off a guy that needed some funds. I guess I know why he wanted to get rid of it.