I second what Jim said. The trigger group is fairly easy to remove, and isn't too difficult to clean. I wouldn't recommend detail stripping it, as this can get very complicated. All you have to do is drift out the two pins in the receiver, and the grouping will pull down out of the receiver. The easiest way to clean it is to soak it in a degreaser for a while, and then spray the trigger group with some compressed air, which should remove the excess degreaser. Check the trigger group for "funk", which could be causing the problem. Make sure you apply some gun oil, and check the function of the trigger while it is out of the gun. You should be able to manually cock the hammer, and it should lock back (without any problems). If its not locking back, then there is definitely something wrong with the sear/trigger/hammer assembly. If it is locking back correctly, re-install and try the gun. I doubt very seriously if the gun is shortstroking, especially if it is ejecting spent cases and chambering live ones. Cleaning the trigger group should solve the problem (hopefully).
