I found a place one line that load 700 gn. bullets for the .500 S&W. They claim 1,200 fps. from a factory handgun. That round has a TKO 3 lbs. less that the max. load listed for a 400 gn. bullet in a .458 Win. mag. in my Serria manual. I don`t really see a need for one of the .50 BMG handguns, but if my .500 S&W doesn`t kill the mice I have around here I may have to give one a try.