"If you're going to include the BFR (which shoots a rifle cartridge), then you may as well include Savage Strikers and T/C Contenders and whatnot;"
No, he specified revolver or auto. So we can't even bring up the .45/70 derringer by American Derringer. Besides, I am sure JD Jones has plenty of stuff that will out do a .300 Win Mag. I guess I should go to the link before asking this question, but what does a .600 Nitro revolver weigh ? The cylinder must be six inches in diameter ? By the way, I am all for the idea that if a handgun is chambered for a given cartridge, it is in fact a handgun cartridge.