I have one here that's going into an early style SMR. It's a 7/8" .50 cal. 42" long. Rifling has six narrow grooves, square cut, with wide lands, and no reamer that marks I could see. Before breeching I always put an aperture in the muzzle of every barrel and sight through looking for concentric rings of light indicating a straight bore. This one looked to be perfectly straight. The outside needs draw filing as do most others. Milling the dovetail slots seemed quite the same as cutting them in a Green Mountain. It'll be interesting to see how it shoots and loads with the narrow groove/wide land rifling when I test fire it before it leaves for it's new home. All in all, it looks like a good barrel.
Ted