Had the same issue in a Marlin 336 35 Remington. Bullet I was using (Lee 35-200-GC) is a bore rider design similar to yours. Wouldn't chamber a PC bullet or required lots of force. Or, if it did, the bullet would unseat after extraction, lodging the bullet in the barrel and dumping powder. When I tried one not PC, it works fine with just a slight bit of engraving on the nose. As suggested above, try a dummy round with out PC. I just shoot mine not PC and if I stay around 1,800 fps or less with WDWW I don't get leading...and, that is in a micro groove barrel.