I do that on the muzzle of all of the rifles I build, not on my blunderbuss though.I use a round needle file to make a center groove on each flat and a triangle needle file to make a small cut on each side of that.Not long flites ,just short ones.Looks great after being browned and as I am loading my rifles I am looking right down onto the design around the muzzle.Different strokes for different folks!Go for it!!!
J.J.