What will you be shooting with it?
If its varmints, a 3- 9x or 3.5-14x or so scope will work well.
You may only be shooting out to 200 now but soon you may stretch it to 500 yards so think ahead on your optics purchase.
If you're shooting coyotes definitely stay with a variable that will have a low power setting.
Close-in fast shots can be difficult with 4x and up.
This would be great on a coyote rig:
http://www.midwayusa.com/eproductpag...278&t=11082005
A reddot for close shooting (in my limited experience) will outperform most scopes.
If you do a reddot, look at the Aimpoint Comp M series. It has butler creek flip-up caps that keep out rain, snow, dust, etc...
Some of the other reddots do not have convenient covers and are exposed to the elements.
http://www.midwayusa.com/eproductpag...434&t=11082005
Sounds like you have a flattop, is this the one?
http://www.bushmaster.com/catalog_xm...VMF16M4ORC.asp