The Ruger #1 comes only in one size.

Ruger made a run of the 1A in .357 Mag about 20 years ago. It was a dandy little rifle. I would have bought one, except that I had a Stevens Mod. 44 1/2 chambered in .357 Mag. at that time. The .357 is quite useful in a short, handy rifle.

Curl