Split a dowell (5/16 or 1/2 diameter) wrap with 0000 steel wool till just tight in the chamber. Chuck the dowel in a cordless drill, keep a little lube on it and check often till chamber is bright. I also do this to remove plastic build up in the chamber. Plastic from the hulls, will build up. It has to be removed or the same jamming will result. Patience and common sense and you can polish the chamber and get rid of your jamming problem.