Thanks Treblig for the Cumming reference - I guessed wrong, I thought it could have been Frederick Barber.

FWIW, on the "big gun" - from my archive :-

" ............We got much pleasure from the visit of the Bakers in 1881......He was well over sixty, but it was easy to relate to that herculean frame the tales of his dominance twenty yars earlier, and the awe he had inspired in the lands of the Senoussi.......Baker used a heavy .577 Express with an unusually heavy charge, and he was still a very fine shot. But it required a man of his weight to stand the recoil of “Baker’s Baby.” I killed a wapiti with “Baby” and the recoil shook every bone in my body. "

Location of meeting was Wyoming.
Rs
K.