RA, expect you'll be OK in a Stevens. Most of the time, those 67MM shells do work OK in 2 1/2" guns. The exception seems to be if you've got an old gun with short, sharply tapered forcing cones. I think it was Charles Fergus who discussed this in a Shooting Sportsman article from several years ago. He had a couple British 12's, one from the 1930's and the other, I think, from the 1890's. And he had a bunch of those 67MM shells--which say right on the box (if they're British) that they're OK in guns with 2 1/2" chambers. They were fine in his more modern gun, but he was blowing the ends off them in his older gun. Appears that the forcing cones were the culprit. He switched to true 2 1/2" shells in the older gun and had no problems.
