Originally Posted by Brue182
Well what I was saying about the lower was based on my ARs being manufactured instead of building my own. P.s. I have a Sig Sauer 516 & 716.
Oh ok. my "store bought" AR is stamped with ".223/5.56" on the lower, and the barrel is clearly stamped '5.56 1/7' the AR that I put together has the same ".223/5.56" stamped onto the lower --indicating that it's a rifle lower and an 18 year old can buy it, but he can only put a 16" barrel or longer on it. the lowers that are marked in a handgun caliber or not marked for any specific caliber are typically sold as "pistols" so only someone who's 21 can buy one, but then you can put a shorter barrel on it. there may be other legalities as well, but that's just my basic understanding of it
anyway, the barrel on the upper I built is also stamped with the caliber, "5.56 NATO 1/9"