Those hard to kill bulls are usually ones that have just been run, climbed a mountain, or in the one case swam a river or lake. When they get thier adrenaline flowing , it takes a lot to put them down. If they are not spoked, and no adreniline is flowing, most calibers from .270 up will put them down bang flop as some say. I know a guy tha kills regularly with a 25-.06. Not my choice, but he does it.
My choice is an .06 with heavy bullets. I have killed elk from 15 yds up to 340 yds with them and the elk have gone down right now, and I usually kill one every year. If you are pushing bullets to high velocities, as magnums do, stay with the premiums, if not, most of the heavier bullets that Sierra, Hornady, Speer , etc will do the job, as long as they are placed in the right spot.
My rifle of choice for next year in heavy timber, just for a change, is a 44 mag carbine shooting full loads of hard cast bullets
