I ran into the same thing with my Black Diamond when I bought the Hornady SST's. Now the Thompson Center 250 gr Shockwaves will go down the barrel. What I suggest is pick up a set of Harvester Crushed Rib or MMP HPH-24 sabots and put the SST's into them. They will then load down the barrel. Shoot them with about 90-110 grains of Triple Se7en 2f and I think you will like the accuracy.