I have a Ruger Mark II, 5.5" bull. I purchased a VERY nice Ultradot 30mm 4dot scope. It doesn't come predrilled fro a scope mount and I didn't particularaly wan't any new holes in the receiver.
I did some research and ended up with a MGW no-drill mount per a variety of people's recommendations. It works, HOWEVER, it's 1) heavy (an additional 2-3 oz), and 2) topheavy (screwing up the balance of a nice pistol/scope).
So, I got rid of the mount, and went with a solow. It's -nice-
It's lower to the bore than anything else, even (I believe) drilled and tapped with rings. That translates to less adjustments of the scope needed at different ranges (a big prob with the MGW).
It's also VERY light, hasn't moved a bit, and has generally been pretty darn slick. It only comes in 30mm, however, and that may be its only drawback (check out
www.solow.com), if you want a 1" scope. Only word of wisdom, if you do go with it, you may need to lightly file a BIT off the bottoms of the rings as they try to bind with the frame, making field stripping tougher. This is remarkably easy to fix.
Good luck, and oh, did I mention I love my ultradot?