If you do a search you will find some intersting stuff. Most important will probably be the titles of a couple of books on building DR's on shotgun actions.

500 Grains has shot a fair number of elephants with his 500NE which I believe is a 3" - the standard.

570 grains at 2150fps is the factory ballistics. I beleive the ballistics of the 3" and the much less common 3 1/4" are the same. I have not shot one but, reportedly, the recoil is stout.

JPK