I went to the range today to get some cheap trigger time. I had loaded some ammo in my usual jacketed brass. The brass has worked well and fine for about 9 times. Since annealing I have fired them either once or twice before today, without trouble (and with good groups.) I had about fourty rounds of corrosive Bulgarian Surplus that I decided would better serve me as powder and bullets. I pulled them, Noting the average charge, and then weight sorted the bullets. When I loaded them I used several different primers behind a charge 3-4% less than the original. I seated the bullets out pretty far, unto my estimation of about on the lands but not quite; I did a quick check to make sure they weren't “jammed” and called it good. I wasn't expecting much, just trigger time. I was firing them in my M39 for jacketed which has a .313 bore - (this gun consistantly groups under an inch to as small as .6” with my “good stuff” using Hornady .312's) The surplus projectiles are .310.
I fired looked at the brass and .......WHAT?
cleaned the chamber and looked in the barrel,,, Fired again,,,,,happened again,,,,,Broke the whole gun down right there,,,, nothing I waited and thought,, put it back together and held the gun away from me - like that was going to do some good - and let another go,, it was fine. I fired the rest and only one other exhibited the dent. the brass was only fired once since full length sizing, but it had been only neck sized since being fired last. The powder seemed really dirty, but i don't remember any trouble with the surplus when I fired it normally.
Any ideas?
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