I know I am going to get the "This Post is useless without photos" reply, but I watched the Gauntlet and froze-framed it when Eastwood handed the revolver to Locke just after stepping onto the bus.

It's a square butt. I tried to do a screen capture and ended up wasting a pile of time and frustrating myself. But yes, it WAS a square butt, at least in that scene.