Really nice looking revolver, Bushmaster, and nice work with it as well.
That group may well move a good bit towards the center by simply blacking the front sight. I competed with pistols and rifle, with open sights, for many years and found early on the importance of blacking the front sight with soot or a commercially available aerosol blacking. There are several theories as to why the group's center will be affected by this practice, but the one I believe in involves strong sunlight from one side or the other of the shooter. A bare metal blade or post that is uncovered will have reflection on the side receiving the strong light, and the other side will be in the shadow. This causes an apparent
shifting of the sight's center to one side, because the eye is more "drawn" to the side with the stronger light on it. This is the main reason for hoods on front sights, not protection of the sight. The sooty covering prevents any reflection and the sight looks the same on both sides even with strong, bright sunlight coming at 90 degrees from the side.
Starting out in competition, and for many years thereafter, I kept a fat lighter pine splinter in my shooting box. Before a match I would light it and use it to black my sight. Later years a commercial aerosol became available to do that, and was much handier. For some reason, people would get upset when I lit that fat lighter stick at the loading bench of a black powder match.
This practice is as old as shooting competitions themselves, and it is still in common use at iron sight matches.