My 450 is very accurate, I took it Elk hunting last year, but didn't have an opportunity to try it out. I would not be hesitant to shoot and Elk with it under 300 yards. After that the trajectory would need a little more calculation.

There is a 450 forum, some of those guys talked about swaging the .458 bullets down to use, but you really need a rifle length gas system rather than the carbine length that the rifles come with. (Even the 20" uppers from BM have a carbine gas system with a mock gas block at the rifle position.)