Assuming 30 cal,(yeah I know about ass u me-ing wish I/we didn't have to assume), which cartridge, 308,n30-06, 300 mag,,,---?
I'll go one further, 300 WSM, which is where I threw down an anchor. 165 Hornady GMX;
Excellent expansion, 100% weight retention good accuracy,(right at 1"). Velocity must be above a certain level, IIRC it's 2200 fps.(Check Hornady's websight, I believe they spell it out.
Oh, and, the GMX is made from Guilding Metal (eXpanding). Which is what everyday bullet jackets are mad from. Those above did not excessively foul my barrel.