How to clear a serious AR-15 jam?

Sounds like something is ajar in the action (hopefully part of the bolt hasn't broken). Then again, maybe you've just got a large piece of debris in there. Could happen to any gun in theory. As for getting the rifle unjammed, some friends of mine in the military have said that they place the rifle upright on the ground (stock down) and kick down on the co cking handle when things are really bad. That would certainly make me cringe if I were doing that to my own gun though. The upper is made of aluminum, so if there's something sharp or bent in there, you could cause a major gash in the receiver. If things were that bad I'd probably be going to a gunsmith that really knows their AR15s.