With hand loads with lead bullets I have gotten sub 4 inch groups with my 9mm storm at 100.
That was with an Aimpoint on sand bags.
http://www.aimpoint.com/
With cheep factory Remington white box it will hold 5 inches at 100.
I have had cheep Chinese red dots and all I can say about them is that they are made for paint guns not for real guns.
Buy American and buy an aimpoint.
The following has a photo of mine with an aim point.
http://thefiringline.com/forums/show...+storm+carbine
and
http://thefiringline.com/forums/show...+storm+carbine