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9mm AR Barrel

Discussion in 'Rifle Country' started by GIJOEL, Feb 23, 2010.


    GIJOEL Well-Known Member

    So here we go, I want to build a 9mm upper, I have a A2 compleat upper and a Knight 2 peice quad rail. I like the dissapator look and I would like to use what i have. The question is does anyone make a 16in 9mm barrel that can be set up for a rifle length fore end? I've looked around and everything out there is CAR or mid length, 9mm is recoil operated so there is no gas tube. Can I just put the FSB wherever I want?
  2. ants

    ants Well-Known Member

    You also need a 9mm bolt. Also, the case deflector is different because the shorter brass ejects right up at the front of the ejection port. Also, you need magazine and mag adapter block that work together.

    Get a mid-length free fload quad rail and you can install it on any 9mm upper. Yes, you can put the front sight base anywhere on the barrel but you gotta drill the holes for the taper pins. Or use a front sight base that uses set screws.

    GIJOEL Well-Known Member

    yeah i'm going with a cmmg bolt and i know about the case deflector, I'm trying to figure out a way to use the knight quad rail that i have, it's not a free float rail so i need the forward mount plate.
  4. ants

    ants Well-Known Member

    You can't just put the front sight base wherever you want, because the diameter of the 9mm barrel is 0.720" except where the FSB goes (it's got a 0.750" shoulder at the FSB location).

    They make complete 16" 9mm uppers in mid-length. I bought one from RRA. I don't know if you can buy a barrel only with FSB at mid-length. Call RRA and ask.

    By the time you buy a barrel, flash hider, and a complete bolt carrier assembly, haven't you already spent more money than the complete upper? My complete upper was $400 shipped from a Gunbroker vendor.

    The carrier on my 9mm is not the same as a 223 carrier. Not only is it cut differently, it's also solid (not hollow) so it's heavier to slow down the blow-back action. Otherwise it blows open before combustion is complete.

    GIJOEL Well-Known Member

    I might just get a compleat upper. I want the rifle length hand guard and sight radius, thats why I need the FSB further out. If I build the upper i'm looking at 500-600 with the bolt. Compleat uppers are about the same, but then a quad rail is another 100-200 for something nicer. If I can use the parts I have sitting on my workbench I will have a nicer upper for the same money.

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