I have one of those oldies and they are neat little rifles. They take the 22 Winchester Auto Rimfire cartridge - not the same as the 22lr. It is a slightly tapered rimfire cartridge that shoots a 45 gn bullet at about 22lr standard velocities. At least my 1903 does - some may be in 22lr, possibly. The rifle was a good design and I think others copied it later for the 22lr. The particular rifle I own won at least one local 'International Flagpole Shoot' back in the early 20s (lololol, but true.) HTH. Mikey.