From what I understand the power belt bullet is under sized. The only part that's touching the barrel it the plastic piece on the back. I've heard of guy's bumping there gun on something and having the bullet fall out the end of the barrel. Switch your bullet to something like th Hornady sst bullets w/easy load sabots. Or try the all lead Dead center bullets. They shoot great out both my T/C Black Diamond and my Bighorn. If you use the SST bullets you should switch to the loose powder, or you should buy the High pressure sabots.
Good Luck