If I could actually hit anything at 100 yds with my iron sights I'd be happy to keep my SKS(s)' factory stock!
I just installed a 'Dead Ringer' Red (& green) Dot on an ATI mount yesterday.
ATI gives you an entire new receiver cover c/w rails to replace your factory one. The whole key to its reliability is the care you take when installing it; it needs to be fitted to your specific carbine.
I took my time, filing, fitting, filing, fitting til I got it perfect. It does not move. It's way tighter than the factory cover was.
The sight is fun to play with and it gives me a much better view of the target.
I went out to the range and just dropped it onto the rails and fired a few rounds. It was on the paper
straight away--a good grouping at 3:00, 6" off centre. That's all I had time for, but I'll adjust the reticle more to the right and see if I can't zero it in real good. I'm not hoping for 1 MOA, but I'd be real happy at 3 (especially if it stays put).
I can still use stripper clips, and the brass still gets tossed without hitting anything.
http://deadringerhunting.com/monteria-red-dot.html
http://www.marstar.ca/dynamic/product.jsp?productid=84401