BlackBruin said:
A reflex sight will work, only weigh 2 ounces or so
I use iron's too on my S&W M17. But if you want to put a red dot on, take BlackBruin's advice. Stick with a small reflex style sight as opposed to some of those honking traditional dot sights.
The main problem you will have is the size of the dot. Stay way from those 8 mill jobbers as they will completely blot out the head of squirrel at 40 yards. Try to find the smallest dot you can in the smallest sight you can. Most of the reflex style types, like Burris Fastfire, while small and very light (like 2.5 ounces) don't come in anything smaller than 3.5 mil.
Some of the bigger dot sights can come with 1 mil dots.
So it's a trade off.
I have a Burris FastFire on a 45-70 guide gun. Works like a charm, especially on moving deer. But that gun will shoot inside the 4 mil dot at 100 yards all day long. Which gives a rifle looney like me cause to ponder switching it for something else just because I want to be more accurate. Haven't yet.....................