I have a Hammerli Umarex 850. I was having trouble chambering a round and ended up taking the bolt housing apart and found a pellet had found its way into the housing and was blocking the bolt from fully chambering a round. Once I put it back together it will not fire. Pulling back the bolt will set the safety but when I release the safety the trigger will pull but not fire. What stupid thing could I have done or forgot to put back into place??