It has a pretty abrupt step like a several of the Parker's I own from the 1870 to 1882 period. That, and an 1874 Sauer Cape gun with a rifle barrel in 20ga x 50 mm is what made me think it might be a brass chambering. I was just surprised that a shot barrel ws chambered for a 2-1/4" cartridge. I was wondering if a 2-1/4" shotshell was ever marketed.