X2 on what contender posted.
the weigand is great for a GP,installed one on my wife's topped with a 30 mm ultradot reddot. she has sent many full tilt rounds down the pipe with zero shift. if this will be a hunting revolver I am partial to the 30 mm tube dot with some scope covers for snowy/drizzle weather hunting. if your going to be shooting targets then you could go with the compact open dot sight. amazon has ultradots for 160$-170$.