The barrel end has a flat spot (figured for some kind of a bore collimator device) but if you align that to the turret axis then those rib thingies are off center.
Now I have found some pics (although probably not the same barrel) with those ribs off center as well as dead center with the axis so I want to know what is right or it's what Russian tank crews feel that works-goes
Any thoughts on this one?

second barrel in line

