I have a cheap-*** Barska 3-9x42 on a quick detach NCstar mount on my M&P15T - for $60, its great! If it works on the big bro, it'll work well on the 15-22 - chances are I will probably end up putting it on it when/if I get something better for the 15T....or maybe I'll just buy another one!
Amazon.com: BARSKA 3-9x42 IR Contour Riflescope (4A Mil-Plex IR…