I have been looking into buying an AR but I don't want one that shoots .223s too high priced for my bank acct.. I have an AK-74 that shoots 5.45x39 ammo (that I have plenty of), and I see that I can buy an AR upper in 5.45x39 here.
Product: M&P15R Upper Receiver Assembly
My question is if I buy this upper, will any lower work with this upper or does it need a specal lower just for that cal. round?