Right cartridge for a B.Hughes snider rifle?

I recently brought a “.45cal snider action rifle” marked B.Hughes on the side plate. Nice tidy sporter.
Unfortunately its not in the expected .450/577.
So far my several lists, CotW, and Gooogle can not determine exactly what caliber it is! Any ideas anyone?

From a chamber cast, the dimensions are
Rim .665 +/-
Base .565 +/-
OA Length 1.635 +/-
Length to start of shoulder 1.05 +/-
projectile .448

My best guess would be .45-50 Peabody. But the rim is too small. So is the base dimension but I know many BP era guns are bored oversize… :-)

Any help?


Have you looked at the 450 #1 Carbine? It is close in the Rim, Base and shoulder location.