The bullet should not be able to turn inside the case. If it's that loose, it could possibly set back upon loading into the chamber. That would greatly increase pressure.
Are you full length sizing your cases? That alone should eliminate any movement of the bullet by making a tight fit. The only other thing I can think of is you may be flaring the case mouth too much.
The 10 thousands variation sometimes occurs. I think that all depends on the uniformity of the bullets and you really can't control that.
Too light for heavy work, too heavy for light work!
Last edited by buckshotshorty; 12-28-2012 at 21:31..