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I've moved your post to the introduction section so you can get a proper welcome and so your post will be seen.
Please take a minute and tell us a bit about yourself so we know a little about who were talking to.
I know our members will have some advice for you.
Wish I could help you with your 3 screw. All the Blackhawks I've ever had have been New Models.
Someone here should know about those old 3 screw models. A call to Ruger's customer service would be another option.
In case you don't know, Ruger has very good CS.