Sir: I have a Bushmaster XM with the 14 1/2" inch barrel and the 2" permanently attached flash suppressor Shorty (not the one listed in the for sale section). I cocked the rifle, fired a round, and then tried to fire a second, and it only clicked. It hadn't chambered a round. It would blow back after the first shot, but wouldn't chamber the next round on its way back into resting position. It would simply slide over the top of the next round in the magazine, sometimes scratching the case slightly, sometimes not touching it at all. I could cock the rifle slowly manually after each shot, watching to make sure it caught the next round, then letting the bolt slap shut the rest of the way, and it would work that way and chamber a round that would fire. But I could never get it to catch the round itself after firing a shot. I tried everything. I made sure the magazines were seated properly. I tried new and used magazines and different ammo including Remington .223 straight out of the box. Same problem. Any help would be appreciated.