Originally Posted by
1874sharpsshooter
That's an old original Knight jacketed bullet with the old formula high pressure sabot. I figured if your bore was loose that might work. I think your bore is about average but definitely not loose because all the others loaded the way they should.
That bullet is probably sabotted with a MMP short black sabot which is .506 and would be awfull tight in a .503-504 bore.