Are these the old green packaged Powerbelts? What weight is on the package? If it is, they are a little wider than the regular Powerbelts. The regular ones have weights of 245/295/345/405s.

Put Bore Butter/Wonderlube 1000in the bottom cup/hollow base of the plastic sabot if your Powerbelt package is the wider, green one. Swab after every 2nd shot with both sides ofa wet patch (Windex)& brass bore brush. Follow with both sides of a dry patch.That should help.