I suspect that it's not chambered for the .45-70. You'll probably have to do a chamber cast to get a good idea what the cartridge is, but generally you'll only find period low wall rifles chambered for pistol cartridges and the small .22/.25 (primarily rimfire) rifle cartridges.
I'm not getting much in the way of real work done this afternoon because I'm thinking about this so darned much.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.