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Thread: Primer punching?

  1. #11
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    Sometimes caused by a firing pin that is too sharp.
    Also, I would recommend this to prevent blown primers from falling into the fire control group and causing a stoppage: http://www.brownells.com/rifle-parts...442-62300.aspx

    Likely also a chamber that is too tight. All the more reason to spend the money and get a Colt, DD, BCM, LMT, Larue, or another well-known brand...in the AR 15 arena, you DO in fact get what you pay for.
    Last edited by XD40Colorado; 07-18-14 at 09:56. Reason: Spelling errosr

  2. #12
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    This is more than likely a CMMG .223 chamber marked as 5.56 or whatever. Get the chamber reamed to 5.56 or replace the barrel with something decent.

    (The firing pin may now be damaged from gas flow from the pierced primers)
    "You people have too much time on your hands." - scottryan

  3. #13
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    Quote Originally Posted by Radioflyer View Post
    I acquired the piece over 2 years ago. I noticed it was popping primers after about 200 rounds (which occurred over the course of several months as where I lived there weren't many rifle ranges nearby I could use at the time.)
    Any chance the first 200 rounds were a different type of ammo? .223?

    Chubbs

  4. #14
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    CMMG has requested I send the upper to them for examination. It will be shipped out today.

    Quote Originally Posted by XD40Colorado View Post
    Sometimes caused by a firing pin that is too sharp.
    Also, I would recommend this to prevent blown primers from falling into the fire control group and causing a stoppage: http://www.brownells.com/rifle-parts...442-62300.aspx

    Likely also a chamber that is too tight. All the more reason to spend the money and get a Colt, DD, BCM, LMT, Larue, or another well-known brand...in the AR 15 arena, you DO in fact get what you pay for.
    I bought this back before the big AR rush and even if it does have a few hiccups, so long as I don't end up replacing too much, I would still say I got a good deal. When it did work, It worked well.

    Quote Originally Posted by Chubbs103 View Post
    Any chance the first 200 rounds were a different type of ammo? .223?

    Chubbs
    I've shot a mix of .223 and 5.56 depending on what was available at the time. The chamber is rated for 5.56

  5. #15
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    Quote Originally Posted by markm View Post
    This is more than likely a CMMG .223 chamber marked as 5.56 or whatever. Get the chamber reamed to 5.56 or replace the barrel with something decent.

    (The firing pin may now be damaged from gas flow from the pierced primers)
    I think this suggestion is a good place to look for a solution to the issue.

    I would try shooting a few hundred rounds of only .223 ammunition, versus 5.56mm, and see if the problem subsides. If you don't see pierced or popped primers, reaming the chamber to 5.56mm would probably resolve the issue.
    Train 2 Win

  6. #16
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    Quote Originally Posted by T2C View Post
    I think this suggestion is a good place to look for a solution to the issue.

    I would try shooting a few hundred rounds of only .223 ammunition, versus 5.56mm, and see if the problem subsides. If you don't see pierced or popped primers, reaming the chamber to 5.56mm would probably resolve the issue.
    I'm not familiar with the reaming process. Can you explain?

  7. #17
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    Quote Originally Posted by Radioflyer View Post
    I'm not familiar with the reaming process. Can you explain?
    Unless you have the tools, headspace gauges and some experience cutting chambers, you are better off not attempting this on your own. This is something that should be performed by a good gunsmith or armorer. The chamber is recut to 5.56mm dimensions.

    Search 5.56mm vs .223 chamber on the internet and you will find enough technical drawings and material to keep you busy reading for quite some time.
    Train 2 Win

  8. #18
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    Col Crocs' and markm's thoughts are the most likely, given the symptoms and the fact that it's CMMG: mismarked or outright out-of-spec chamber.

    Perhaps the most familiar or common reamer is the Ned Christiansen 5.56 chamber reamer. Find a gunsmith who has one, have him take it to your chamber. As T2C noted, if it's a .223 chamber, or otherwise tight, it'll remove material from your chamber and make it a true 5.56.
    Contractor scum, AAV

  9. #19
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    Quote Originally Posted by T2C View Post
    Unless you have the tools, headspace gauges and some experience cutting chambers, you are better off not attempting this on your own. This is something that should be performed by a good gunsmith or armorer. The chamber is recut to 5.56mm dimensions.

    Search 5.56mm vs .223 chamber on the internet and you will find enough technical drawings and material to keep you busy reading for quite some time.
    Oh I agree I have no intention of attempting this, I was just curious about the procedure. I have since sent the upper to CMMG for troubleshooting. My thought is that If they built it, they can fix it.

  10. #20
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    Quote Originally Posted by Radioflyer View Post
    Oh I agree I have no intention of attempting this, I was just curious about the procedure. I have since sent the upper to CMMG for troubleshooting. My thought is that If they built it, they can fix it.
    That's probably the best way to handle it.

    As a rule, I will shoot 5.56mm and .223 through a 5.56mm chamber and only .223 through a .223 chamber.
    Train 2 Win

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