From my very limited understanding of and reading about proof rounds, one should expect a standard powder charge under a grossly-overweight projectile (a .50 BMG example I found cited using a 25% heavier bullet) compared to the standard bullet-weight for the chambering in question, in the aim of deliberately increasing chamber pressures well beyond the norm. So 320 vs 230 grains of bullet, in this context, rings some (albeit precarious) bells. "Let's see if the thing blows up!"
Edit: Of course your math is correct, and mine is all ahoo. 15 grams = 230 grains. My damned brain transposed some digits. Mea culpa.
Last edited by Fudd; 10/24/23 07:57 PM.
