Buffalo rifle generally refers to large-calibre, generally single-shot black powder cartridge firearms which were used to hunt the American Bison to near-extinction in the late-19th Century.
Three types of rifles in particular were used by professional bison hunters, namely the Sharps rifle with a 90, 100 or 110 grain powder load, the Springfield Rifle and the Remington No.1 rifle otherwise known simply as the Rolling block.
[1] The Sharps was the favorite among hunters because of its accuracy at long range.
[2]