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Thread: Anybody know the actual chamber size of my RRA LAR15

  1. #11
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    You can take a cast of the chamber and measure it, or if you want a 5.56 chamber, just use Ned Christiansen's 5.56 reamer. If you get metal out, it weren't 5.56.

    MBR

  2. #12
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    The reamers are made on the larger end of the spectrum for 5.56mm NATO. So on many barrels Neds reamer will remove some metal from some chambers including Colt and LMT.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  3. #13
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    I was aware of the chamber cast, but I'm still wondering how close you can measure leade dimensions. I guess you can get pretty close, and for certain you can measure throat diameter accurately. so that would be a good indicator.

    Ned's chamber reamer is a tad bigger than 5.56 IIRC. I believe he's posted that, either here or on his website. Just because you get some metal removal, I don't think it's accurate to automatically infer that the chamber just reamed was a SAAMI chamber.

    Maybe Ned can chime in here and provide a clarification.

  4. #14
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    If you reamed the chamber, wouldn't you remove the chrome lining? Although that's probably a secondary concern if you're trying to size it. I put a MI 2 piece forearm on my RRA. I had such trouble getting the lower 1/2 on, I needed extra hands. I can't get it off by myself, but Gotm4, I'm further confused by your list of codes for ".223" barrels. I thought we were talking 5.56 chambers. My barrel is chrome lined 10.5". There's only one code listed for that so I expect that's what I'll find when I get the handgaurd off.

  5. #15
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    Quote Originally Posted by CCFP View Post
    If you reamed the chamber, wouldn't you remove the chrome lining? Although that's probably a secondary concern if you're trying to size it. I put a MI 2 piece forearm on my RRA. I had such trouble getting the lower 1/2 on, I needed extra hands. I can't get it off by myself, but Gotm4, I'm further confused by your list of codes for ".223" barrels. I thought we were talking 5.56 chambers. My barrel is chrome lined 10.5". There's only one code listed for that so I expect that's what I'll find when I get the handgaurd off.
    Yes, but if you are popping primers or experiencing other "over pressure" signs, then it's either ream that bad boy and lose a bit of chrome or relegate yourself to low pressure ammo.

  6. #16
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    Quote Originally Posted by MX5 View Post
    My RRA bbl was .223 - had to finish ream to 5.56.

    Yep. IMHO, most RRA barrels are somewhere between .223 and 556.



    C4

  7. #17
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    Quote Originally Posted by gotm4 View Post
    The reamers are made on the larger end of the spectrum for 5.56mm NATO. So on many barrels Neds reamer will remove some metal from some chambers including Colt and LMT.

    Mine has never removed anything from Colt 6920's or LMT's (yet).


    C4

  8. #18
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    RRA 5.56 chambers trend toward the small end (at best), and the problems/indications of tight(er) chambers have been observed in several.

    I've reamed chambers with Ned's reamer, including chrome lined. No problems. As on his website, it removes chrome that will erode anyway.

    I've reamed Colts, too, but removed only a tiny bit of material.

    Ned's reamer is must have for maintainers, especially those infected by "good-as."
    2012 National Zumba Endurance Champion
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  9. #19
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    Quote Originally Posted by C4IGrant View Post
    Mine has never removed anything from Colt 6920's or LMT's (yet).


    C4
    Interesing. Colt and LMT combined I've reamed about 100 barrels. Mine has removed some metal from all of them. Some more than others.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  10. #20
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    Quote Originally Posted by gotm4 View Post
    Interesing. Colt and LMT combined I've reamed about 100 barrels. Mine has removed some metal from all of them. Some more than others.
    I get a few small flecks of chrome. I do not classify that as removing anything substantial. Our reamers might be slightly different.


    C4

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