Never had to use it, but I carry an AK in 7.62x39 all the time anymore. I still have some 150 grain Cor-Bon ammo for it that I think runs about 2300 fps with 1762 ft. lbs. of energy if I remember correctly. I don't think they make it anymore, but they may still make the Hunter DPX that has 1445 ft. lbs. at 2300 fps. I should look around again and see who is making what for it.
Generally there is always two of us when I'm out, and my friend carries the 12 gauge. I still think that a 12 gauge is the better option obviously if you can hit with it quickly. A Benelli M4 is in my future at some point for this reason.
For now, I feel completely comfortable with the AK and that I have somewhat good shot placement due to the relatively light recoil. Most of all I trust that it will always go bang. And if shit goes sideways, it will be going bang 40 times. I just seem to be able to get the AK up on target faster and stay there than with my 870 pump. I need to go take some training classes with 870, and that would help.