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Is this a bolt malfunction?

Discussion in 'GATE AR-15 Forum' started by Eric1911, Jun 2, 2010.

  1. Eric1911

    Eric1911

    98
    0
    Mar 19, 2007
    Texas
    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.
     
  2. Constructor

    Constructor Moderator

    552
    5
    Dec 10, 2009
    Roaming
    It sounds like short stroking, just place 1 cartridge in the mag, chamber and fire.
    Does the carrier lock back on the mag catch after firing? If not then it is short stroking and not going back far enough to catch the rim of the next round.

    Remington UMC and Federal eagle are known to be weak, try Winchester White box (XM193) those are full power loads.
    There are several things that could cause short stroking, sometimes it just needs to be lubed well but keep the bore dry(no excess oil) If it has an H2 buffer you may want to go to a lighter standard carbine buffer. If the mags are stuffed full there could be too much pressure on the carrier as it slides over, load the mags to the top and remove one round as standard practice. The gas block may not be in line with the port in the barrel and as a last resort the port in the barrel may need to be enlarged, it's easy to do but not really reversible so that would not be the first choice when looking for a fix.