I agree with HighDesert, you should look into a DPMS R-15. They are much cheaper than a bushmaster or a rock river and they shoot very well. Guns and ammo (or a similar magazine, not sure) did a test on the DPMS utlralight 16" which most would assume is their least accurate gun due to the short and very thin barrel. They averaged under 1.5 inch groups at 100yds. If you go with a stainless bull barrel you will be much under that.

Good thing now is you can go and have a barrel treated with gunKote or dutacoat and cheaplyturn a stainless into a matte black.