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Thread: Bolt not locking to rear

  1. #21
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    Quote Originally Posted by Iraqgunz View Post

    2. Check the things we have told you to check. Gas block, FSB, etc... for gas leakage. Make sure that the bolt carrier key is tight and the screws are staked. Also, check your gas rings and make sure they are tight.

    3. My guess is that you have a standard buffer. This can be identified by looking at the face of the buffer. It will either be plain, or have an "H", "H2", etc...I would get an "H" buffer.
    IG, I have a couple questions regarding your post. My gun runs fine, so this is purely for the OPs help and my information. I'm interested in guns and cars for a similar reason: mechanics. You are a wealth of information, so I'm going to start asking you questions rather than just always reading your posts.

    How would somebody check for leakage from the gas system? I have heard how to check the rings many time, but I'm unsure of how to check for leakage from the FSB and gas tube and block.

    Is the idea behind using a heavier buffer to slow down the BCG enough for it to catch the follower which might not be fast enough? If that's the point, would that mean the system is over-gassed assuming the magazines are functioning normally?

  2. #22
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    Quote Originally Posted by markdh720 View Post
    Is the idea behind using a heavier buffer to slow down the BCG enough for it to catch the follower which might not be fast enough? If that's the point, would that mean the system is over-gassed assuming the magazines are functioning normally?
    We're approaching the "overthink" zone.

    A heavier buffer does a few things... Holds the bold closed a little bit longer(thus extracting the empty at a little bit lower chamber pressure), slows the cycle rate down, reduces recoil, and reduces bolt bounce.

    Many aftermarket carbine barrels are indeed over-gassed.
    Last edited by markm; 07-07-10 at 22:23.

  3. #23
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    Quote Originally Posted by markdh720 View Post
    IG, I have a couple questions regarding your post. My gun runs fine, so this is purely for the OPs help and my information. I'm interested in guns and cars for a similar reason: mechanics. You are a wealth of information, so I'm going to start asking you questions rather than just always reading your posts.

    How would somebody check for leakage from the gas system? I have heard how to check the rings many time, but I'm unsure of how to check for leakage from the FSB and gas tube and block.
    -----------------------------------

    I'd think you could see soot on the silver Gas Tube but to be sure I'd use a clean q-tip and wipe the area where the gas tube enters the FSB (or Gas Block). Wipe the black on black areas around the FSB and the barrel to see if there is soot.

    I've had carbines with SS barrels that you could see soot coming out from under the Gas Block and they worked fine, so I'd think it would have to be a pretty obvious leak to hinder the action.

    A wild guess, I'd say it was the mags... but we'll see.

  4. #24
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    Quote Originally Posted by markdh720 View Post
    IG, I have a couple questions regarding your post. My gun runs fine, so this is purely for the OPs help and my information. I'm interested in guns and cars for a similar reason: mechanics. You are a wealth of information, so I'm going to start asking you questions rather than just always reading your posts.

    How would somebody check for leakage from the gas system? I have heard how to check the rings many time, but I'm unsure of how to check for leakage from the FSB and gas tube and block.

    Usually the leakage will look like a balck-ish-brown rust color. It will usually manifiest itself near the FSB where the tube enters and can also occur around the barrel where the FSB itself is located.

    As for checking the gas rings, it is quite simple. You clean the BCG and then re-assemble. Extend the bolt and then stand it on a flat surface (the face of the bolt) will be face down. If the carrier collapses onto the bolt, then your rings are worn and need to be replaced.


    Is the idea behind using a heavier buffer to slow down the BCG enough for it to catch the follower which might not be fast enough? If that's the point, would that mean the system is over-gassed assuming the magazines are functioning normally?
    I had to use an H2 buffer in order for my 11.5" SBR to lock back reliably after every round. So in this case a heavier buffer may work. Unfortunately there are alot of variables here. IMPO this company (Predator Arms) is not dialed in enough to be producing custom AR's. I would very much like to know what parts they use to build their stuff. Things like the barrel, bolt, etc....



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  5. #25
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    It all depends on your set up. I like the Springco springs. I also won't buy buffers from dubious companies, i.e. Bushmaster, DPMS, Oly Arms, etc...I get either BCM or Colt buffers.

    Quote Originally Posted by chavez_e_chavez View Post
    what would be a good buffer and spring to get?? i think i just have a generic one...Thanx



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  6. #26
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    If you are running fairly new production Magpul P mags with the Light green (Foliage Green) followers, this may be the problem.
    These new followers don't come up as high as the older ones and some guns might not lock open on the last shot.

  7. #27
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    mnoe82,
    Have you been able to find the cause of your bolt not locking to the rear?

  8. #28
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    Not yet. It's been a crazy few days, but I've got some free time today. I'll take some pictures.

    I got in touch with the place where I got it. One of their people said they may have to increase the size of the gas ports at the gas block. They said they would re-stake everything once they're certain its functioning correctly. We'll see.

  9. #29
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    My opinion is quite amateur so take it for what it's worth.... but I think the last thing I would want is the maker opening up the gas port further. After all, it was functioning correctly for a while, right? And it's not as if the gas port shrunk between then and now. Add to that the consensus here that many commercial AR's already have overgassed systems, and I'd be leery of such 'corrective' steps.

  10. #30
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    Before you start doing anything serious i would look at you bolt catch. One of my ARs had the same problem you explained. The problem ended up being an out of spec pin for the bolt catch. Once i drove the pin out and put a mil spec one in everything worked fine. Hope that helps

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