These dies are supposed to set the shoulder back slightly more and size the body smaller for use in semi auto, pump and lever guns. I am thinking of trying a set for loading my 223 ultra varmint, I have polished the chamber a few times, but still get stuck cases after my brass has been loaded two or three times. I have never had a stuck case with factory ammo or the first time loading new brass, so im thinking these dies might be the awnser, and i dont think accuracy will go away, because my gun shoots the same groups with new brass and older brass. Has anybody tried these dies?