As far as picking different weight bullets, you have to try some and see if your barrel likes them. My rifle barrel likes the 165's. That is what I get the best accuracy with. Your accuracy with lighter bullets may depend upon your barrel twist. I have a .308 that will handle 110's. But my .30-06 wont. So before anyone goes and invests in 100 rounds of something other than you know works, I would say try a few and see if you can get that 300 yard accuracy that you need from it. The hunting shows are full of long gut shots that lets the animal run a half a mile before it dies. I'd suspect that the hide and horns are alll that are salvageable from those.
Check your twist, depending upon the rifle year of manufacture and brand, the .30 cal twist could vary from 9 inches to 12 or 13 inches. The longer twists will handle lighter shorter bullets. The shorter twists like longer bullets. It is a matter of physics, not opinion.