And mine - a model 1876 Carbine, altered and re-chambered to .450 Alaskan for BP and Nitro for Black loads. The model of 1876 had a .457" groove diameter, with a .436" bore. After 40 polishing fire lapping rounds, the bore is .437" and the groove diameter is .458". Now, the bore shines, whereas- prior it looked like a sewer pipe.