idahoe, I'm a 300 UM shooter and have never crimped. I get excellent accuracy and have never had a problem with bullet shift. It goes without saying, I don't shoot any compressed loads either. Don't know why you'd need to either, you're already dropping anywhere from 88 to 100+ grains. If you need to load the big 300 to compressed, you should probably buy a larger caliber, IMHO. Several years ago, while working up loads for my 7mm Mag, I did experience (over compressed loads), some bullet slide. In that particular situation, I did put a very slight crimp on. Again IMHO, crimping = pressure, and deserves all the extra care you can muster.