Dee
I have an UltraDot mounted on a Redhawk with thousands of heavy loads thru it, and it has held up fine. Manual on / off, and manual dot intensity. Does not have the battery life of an Aimpoint, but costs a lot less, and is durable.
On one of my M4's, I mounted a 2x7 scope, using a rear Burris ring with a weaver type mount on its top ring, then mounted a Burris FastFire holographic dot site to that. It is primarily as a back up sight to the scope, but is accurate at reasonable ranges, and fast to use. One drawback to it is having to slightly raise your cheek weld on the stock because of its high mounting location. Still, it is fast at close range.
If you prefer a tube type sight, you could probably mount a small one the same way. I don't like the idea of mounting a red dot type sight as the only, or primary sight on a rifle that has the capability and precision to make 300 / 400 yard hits, unless it is a dedicated close quarters combat weapon..
Larry