Check the front of the cylinder. If after firing several rounds and you have a "lock up" check to see if there are scratches on the face of the cylinder. It is not unusual for debris to build up enough to bind the cylinder on the back of the barrel. It takes only a little bit make it impossible to pull the trigger. Then when you open it up, it works fine. This most often occurs when you have developed endshake. Repair endshake and no more problems.

__________________
Richard Gillespie
FBINA 102