I'm looking to get an M4, and trying to figure out the cheapest way to acquire it. For a Stag Arms complete lower reciever (Identical to RRA) with Rock River Arms parts kit and Rock River Arms 6 position collapsible stock? $208 with this to go with it http://www.model1sales.com/item-detail.cfm?ID=UME160&storeid=1&image=um416pre.gif or should I get just the stripped lower for $85, and get a kit somwhere else? was thinking about getting this http://www.model1sales.com/item-detail.cfm?ID=KCEM46&storeid=1&image=carm416pre.gif Someone help me out here, as I know jack squat about these types of rifles. What's the difference between an A1 and an A2 flash hider, and what's the difference between .223 Rem and 5.56 NATO?