Sorry to hear of your problems with Powerbelts. I personally have never shot a deer with them, so I have no way that I can offer a suggestion to improve your performance.

Its hard to go down in powder when your getting great accuracy with something. The fragmenting is probably due to the high speeds of the bullet, but then if they do not shoot good with a small charge, they are of little use that way.

Good luck in the future hunts with them.