RE: revolver calibers
Why not just get a .460 and be done with it? Shoot .45 Colt in it until you can handle .454 and then when you are ready you can move to .460 and shoot anywhere from 0 to 200 yards at the same point of aim. However, any Ruger wheelgun .41 and up will do very fine.
I am curious if the regulations stated .22 centerfire only, which would exclude .22 rimfire.