I have a couple of photos of Nate. The only thing I can tell you is this. In both photos Nate carried 2 Colt Peace Makers. As for as caliber I do not know. I heard that he used a .44-40 rifle and handgun combo. Many yarns were spun around Kaycee, Wyoming and the Big Horn Country. You could hardly visit an Elk Camp years ago with out hearing a story about Nate or Tom Horn. Its a Wyoming thing you know.
RR