Have not had a jam while shooting. I realize I have put a poor number through this gun. Any more problems and I will try bigger balls. We have a shoot coming up on the 27th. Will probably get 100 or more shots. I had a good time today, loaded and shot, only the one ball coming up. Will have to look into the chamfering. I have read about it but it seems to me it will make matters worse, opening up the chamber.