A 250-260 gr bullet at 1100 fps will pretty much handle anything in north america with ease. The heavier bullets are just added insurance. That 325 gr bullet at 1325 fps that Greg S. mentions is what I used a few months ago to take a Cape Buffalo in Africa. The first shot was complete penetration (water quenched) dropped it straight down, the second shot really wasn't needed but it stood back up & a second shot put it back down on all fours.
Heavy bullets have there place on really big stuff but I've rarely recovered a 260 gr bullet on elk or bears in 50 years.
Dick