This is a most unpleasant combo. I can only fire a few of these before I have to stop. It just plain hurts. And leaves me with a sore cheek and a mild headache.

[Linked Image from i.imgur.com]

666 grain slug at 1,604 fps in a gun a little over 7lbs generates about 64 ft/lbs of recoil energy. More than a 10 gauge 3.5" 2 1/4" load at 1,200 fps in a 10.5lb gun. That's several ft/lbs more than a .458 Win Mag 500 grain at 2,100 fps in a 9lb gun.

Just about any 12 gauge 3.5" heavy load will generate more recoil than a lot of the African big bores.