I am using mine on a Ruger Mark III 5.5 bull barrel. I shoot in a 22 league on Tuesday nights. We shoot 3 slow, 3 timed and 3 rapid at 50'. Mine is a Truglo 2x40. If you want to shoot in compitition you might check to see if they accept magnification or not. The league I shoot in doesn't care. I am new to shooting and have an eye injury from 20 years ago so thats why I bought the 2x. The red dot helped a great deal for me and everybody in the league has one, but many different brands. If I was going to put one on something larger than a 22 I wouldn't buy a cheap one. If you buy one let us know what you bought and how you like it.
Rusty