I am very interested in building a 45acp fed AR. I want to build it from a Eagle Arms Poly 15 lower, a Hahn Precision Greasegun Mag block, and Hahn Precision Sub Caliber Buffer, and Oly upper. Is there a special hammer I need, or would I use a 9mm hammer? What else would I need to make it run (other than grease gun mags and ammo)? The people that are running similar carbines, how reliable are they? Thanks for any help!