Slug and double check bore diameter if you can. You may need to be using larger diameter bullits then .355-.356, that is a 9mm size. That could be your problem. And make sure to check cyl. throat diameters for bullit match.
If you can get your hands on some larger bullits give um a test try, before you start changing out bbls. Try everything you can first-my suggestion.
wont hurt nothing. Where are you located?