Before I disassembled this gun and thinned the front spacer, I think I would load some 300 bullets and try them in it. You don't gain much in going from 300 up to 350 grains. 300's are enough for about any big game on this continent. The only time I would go with a heavy bullet would be to hunt big bears or American Bison. Those two, you want to hit with everything your gun can stand.
Bob H.