As elknut is eluding to you may as well throw those energy numbers right out the window. There is sooooooo much more to it than nust energy levels.

Bullet construction being one of the biggest. While 1500 foot pounds may be adequate for a soft expanding bullet you will not need nearly that much with a 45 caliber, heavy, hard cast bullet at lower velocity that does not expand but uses its weight and wide meplate to penetrate and create the wound channel.

Twogreat examples would be from Double Taps ammo. Their335 grain WFNGC at 1600 fps or thier 360 grain WFNGC at 1500 fps.