Don't sell Primary Arms short. Their products get great reviews on AR15.com and other AR forums. I ran a PA M4 on my AR for about three years before I just had to have an Eotech. Put an XPS2-0 on the AR and honestly I can't tell enough difference to justify the $350 difference. But, that's just me.
yes put em on there but make sure its blue locktite can pick it up any walmart or any hardware store even walgreens and cvs should have some.