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Thread: Downsides of a Non-Shrouded Firing Pin?

  1. #21
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    Unhappy

    Quote Originally Posted by gotm4 View Post
    I've not yet met the AR that I can't get a M16 BCG group to work in, other than a sear blocked Colt lower......just sayin'.
    Oh, I have no doubt. The OP's gun, being a Colt, will most likely be a one for one switch. I didn't mean to start anything.

    As for my franken mess, I'll figure it out eventually. I hadn't thought to replace the gas tube. Maybe the gas port is to small and the gun is under gassed rather than the mor common over gassed.

  2. #22
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    Quote Originally Posted by Tweightwee View Post
    The popped primers happened with both BCs and both bolts in both BCs. But only with the Q3131A, and not with Privi or the, I misspoke earlier, LAKE CITY "green tip". I suspect the IMI loaded Winchester is a little hotter than other 5.56 ammo and is unforgiving on "tight" chambers.

    The only malfunction I get when using the new BC and NOT using the Q3131A is short stroking. The gun does not pick up the next round, closes on an empty chamber and does not lock open on the last round.

    I do want to find a Ned Christiansen reamer to resolve chamber problems beyond doubt.
    As said popped primers is a common sign of an AR with a tight chamber.
    Classic short stroking is not enough gas. This doesn't necessarily mean the gas port is too big or too small. Most times it's a gas leakage problem somewhere meaning leaking at the gas block, gas tube, or carrier key.
    To test for short stroking load 1 round per mag, seat the mag, chamber the 1 round and fire. If the gun doesn't lock back with 5.56mm NATO pressure ammo and when the rifle is properly lubed 99.9% of the time it's short stroking.

    It could be overgassed and not picking up the next round nor locking back because bolt velocity is so fast that the mag cant' keep up with bolt. This is rarely ever the case.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  3. #23
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    Quote Originally Posted by gotm4 View Post
    As said popped primers is a common sign of an AR with a tight chamber.
    Classic short stroking is not enough gas. This doesn't necessarily mean the gas port is too big or too small. Most times it's a gas leakage problem somewhere meaning leaking at the gas block, gas tube, or carrier key.
    To test for short stroking load 1 round per mag, seat the mag, chamber the 1 round and fire. If the gun doesn't lock back with 5.56mm NATO pressure ammo and when the rifle is properly lubed 99.9% of the time it's short stroking.

    It could be overgassed and not picking up the next round nor locking back because bolt velocity is so fast that the mag cant' keep up with bolt. This is rarely ever the case.
    If it were a gas leak foward of the reciever, wouldn't it short stroke regardless of the bolt carrier? With the unshrouded BC its been reliable except for with the one ammo type.

  4. #24
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    Quote Originally Posted by Tweightwee View Post
    If it were a gas leak foward of the reciever, wouldn't it short stroke regardless of the bolt carrier? With the unshrouded BC its been reliable except for with the one ammo type.
    It sounds like you might have more than one thing going on. First thing I would get the chamber reamed to a 5.56 chamber to stop the poped primer issue then retest with the 5.56 pressure ammo. If you still have problems with short stroking and the gas key does not show any signs of leakage I would replace the gas tube with a BCM gas tube. It is cheap and not too hard to replace then retest.
    Also listen to GOTM4 and try to give him accurate detailed info I have found out that he does know his sh!t

    One more thing is the gas tube retaining pin in the fsb?
    Last edited by Thomas M-4; 07-04-09 at 00:27. Reason: just to add the gas tube pin thing

  5. #25
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    Quote Originally Posted by Thomas M-4 View Post
    It sounds like you might have more than one thing going on. First thing I would get the chamber reamed to a 5.56 chamber to stop the poped primer issue then retest with the 5.56 pressure ammo. If you still have problems with short stroking and the gas key does not show any signs of leakage I would replace the gas tube with a BCM gas tube. It is cheap and not too hard to replace then retest.
    Also listen to GOTM4 and try to give him accurate detailed info I have found out that he does know his sh!t
    Copy all.

    I'm not trying to be difficult. I think I was still typing when you two were posting. As you can see I'm new to the posting on the internet.

    Thanks to you and GOTM4. I do appreciate your help.

    The barrel was a heavy 16" and I had ADCO reprofile and chop it. They had to dismount the barrel to do that. Then re-park it and reinstall. Does that require a new gas tube? I just checked, the pin is in the FSB.
    Last edited by Tweightwee; 07-04-09 at 00:43. Reason: I forget things

  6. #26
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    Quote Originally Posted by Tweightwee View Post
    Copy all.

    I'm not trying to be difficult. I think I was still typing when you two were posting. As you can see I'm new to the posting on the internet.

    Thanks to you and GOTM4. I do appreciate your help.

    The barrel was a heavy 16" and I had ADCO reprofile and chop it. They had to dismount the barrel to do that. Then re-park it and reinstall. Does that require a new gas tube? I just checked, the pin is in the FSB.
    What is the new length now? [different lengths have different gas port size requirements]
    Process of elimination is how you are going to get your rifle running as it should.
    To me it sounds if you have 2 problems going on at the same time. The popping primer issue needs to be fixed first. When you can run 5.56 pressure ammo then you can reliable test for a possible under gas issue.

  7. #27
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    Quote Originally Posted by Thomas M-4 View Post
    What is the new length now? [different lengths have different gas port size requirements]
    Process of elimination is how you are going to get your rifle running as it should.
    To me it sounds if you have 2 problems going on at the same time. The popping primer issue needs to be fixed first. When you can run 5.56 pressure ammo then you can reliable test for a possible under gas issue.

    Will do.
    The barrel is now 14.5" plus a Phantom. I've been running a H buffer also.
    Just for clarity, the Privi M193 IS 5.56 pressure, correct?
    Thanks

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    The back of those half-C carriers can start to wear a path in your upper receiver over a period of time as well.

    If it's a gun that'll see high round-count, I'd replace it.

  9. #29
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    Can you elaborate on that? I have a sear blocked Colt lower and as a result run Colt semi circle BCG. However, I have been itching to cut off the upper part so I could use FA BCG.

    Quote Originally Posted by RealFastV6 View Post
    The back of those half-C carriers can start to wear a path in your upper receiver over a period of time as well.

    If it's a gun that'll see high round-count, I'd replace it.

  10. #30
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    Quote Originally Posted by andy t View Post
    Can you elaborate on that? I have a sear blocked Colt lower and as a result run Colt semi circle BCG. However, I have been itching to cut off the upper part so I could use FA BCG.
    Basically you have a C traveling inside of an O. Eventually, you'll see two lines inside the upper where the two rear bottom edges of the carrier is impacting the upper receiver.

    Not sure how to elaborate more. It's not really a big deal, but it's inevitable.

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