If your factory rings are "Brand New and Unused" you can contact Ruger and swap them out for 30mm ones. That is the road I went down with my 480 Super RedHawk. It has a 30mm UltraDot mounted on it. If buying again today I would have went one more step up and ordered a 30mm MatchDot II. The main advantage when used on a SRH would be the additional 2 MOA Dot Size for Low Light. It produces less bloom. If you looked through both a 1" "25mm" as well as a 30mm at the same time to get a comparison. You would go with a 30mm. If your rings are used and cannot be traded for 30mm ones is a big factor.
FROSTY; the following link shows my SRH with an ultra-dot in factory rings. I'm still struggling with photo posting, so excuhttp://www.handgunhunt.com/photopost/data/500/454_finished_web_2.jpgse the link. Thought it might help.