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Thread: Bushy buffer chatter marks

  1. #11
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    I you have the circular wear on your buffer it's typically from the rough finish or a sharp edge of the carrier, almost always there's a sharp edge at the bottom groove. If you're buffer is getting chewed up on it's outer edge really bad (looks like someones beat it up with a chisel and hammer) it could be that the buffer detent hole in the lower receiver is machined too far rearward which doesn't allow the carrier to push the buffer off of the detent when the upper is assembled on the lower.

    I had a early Essential Arms lower receiver that had this problem (my first AR in 1987).
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  2. #12
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    Hello All. I ran into this problem several years ago on a NFA FA build we were doing. The Buffer is colliding with retaining pin and here is what we found out. Out of Mil Spec receiver, i.e., the buffer stop plunger hole is not where it should be. The buffer plunger is too far back, which allows the buffer to collide with it as it cycles. Batters nifty little dents in the buffer face. And, it's not uncommon. I saw several incidents of this when I was in the Army. Most of the damage was slight and caused no problems in those weapons. However, the FA build we did was just trying to batter a good 1/16" off the buffer. Two ways we found to fix.
    1. (What we did) Have a machinist cut a 45' bevel on the outside of the face of the buffer for clearance. Not too much, as the buffer must have enough contact with the bolt to operate or you get the same problem with the bolt carrier battering the buffer. Just enough clrearance that the buffer doesn't get beat to death. Oh yeah! Left unchecked, the buffer will beat the retaining plunger to death, also. Worst case scenario is the buffer beats the retaining pin hole out of round and the receiver becomes expensive scrap metal.

    2. Brownells sells a stick-on nylon pad for the buffer face that, once stuck on properly, takes the abuse. I don't know if the pad will stay put for an intense shooting session but knowing modern adhesives, I think that might work well.

    Best fix-and I hate to say this, replace the receiver. Not what you wanted to hear, I'm sure. Sorry and good luck. If I can be of help, let me know.
    Ofc. Lewis
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  3. #13
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    Oly made some bad uppers that would seat the barrel extension far enough forward to allow the buffer to contact the retainer pin.

  4. #14
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    A picture would be real helpful.

  5. #15
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    Colt LE6920 at 5000 rounds. Wear reached this point and ceased. Normal, or at least not uncommon, and not a problem unless material is being removed unevenly or there's other anomalous wear.

    All else is indicative of a more significant problem, and requires prompt attention.

    2012 National Zumba Endurance Champion
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  6. #16
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    If you have a lower that's out of spec and the hole is machined too far to the rear you can assemble the upper on the lower without a buffer retaining detent and spring at all. It's a pain in the ass to assemble it that way but it can be done. I've seen some competition shooters do it.

    Skintop911 that's a good pic of normal wear.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  7. #17
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    Quote Originally Posted by Heavy Metal View Post
    A picture would be real helpful.
    Will work on this, will either use our Nikon 35mm and elect for a CD or will try to get my brother's digital again, another problem, I tried to post a pic of my LMT a while back and could not. It seems the pic was too large to be downloaded here.

    gotm4
    I you have the circular wear on your buffer it's typically from the rough finish or a sharp edge of the carrier, almost always there's a sharp edge at the bottom groove. If you're buffer is getting chewed up on it's outer edge really bad (looks like someones beat it up with a chisel and hammer) it could be that the buffer detent hole in the lower receiver is machined too far rearward which doesn't allow the carrier to push the buffer off of the detent when the upper is assembled on the lower.
    Felt of the rear of the carrier tonight, could feel no burr at all, including the bottom groove. However the edge at the groove was sharp but did not appear to have and burrs where it would contact the buffer face.

    Check it out yourself!...

    Slowly close your receivers and watch the buffer get pushed back as the carrier slides onto it!

    I swear! The retainer is only there for when the gun is appart!
    Could only detect a very slight release of pressure off the retaining pin when doing this, compared it to my LMT and could detect no difference between the two (with my calibrated eye of course (we joke about this in the auto ind.))

    Generally we see this with cheaper buffer bodies not made per the mil-standard. Very few companies use the mil-spec bodies. The short list as I know them:

    Colt
    LMT
    BCM
    G&R
    Stag

    I am sure there are others, but these are the ones I know for certain.



    C4
    I tend to lean in this direction at the moment, but am not totally convinced as yet.

    I only noticed it this Sat after a short (90 rnd) session, did not notice before. It seems when this happens it does so quickly. Could it be a cheaper buffer material that, when the surface hardness gives up, the marks appear quickly? The BM is probably approaching 1000 rnds now, have not had any problems with the LMT but it has only had about 300 rnds through it (estimated). It may be a few days before I can get any photos of it at all but will work on it. I hate to drag this out but I am really getting curious about this condition and it's cause.

    Thanks for all the help

  8. #18
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    Quote Originally Posted by Heavy Metal View Post
    Oly made some bad uppers that would seat the barrel extension far enough forward to allow the buffer to contact the retainer pin.
    There was a guy with a DPMS lower doing the same thing. His buffer detent hole was egging out like a muther!

    I wish I could remember what thread that was.

    ****in' JUNK LOWERS!
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  9. #19
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    This is interesting to me since my new Colt 6920 with a 06/08 barrel has marks on the buffer as well. It's never been fired by me and only appears to have been test fired. I felt the back of the bolt carrier and couldn't feel any burrs on it. I'll post picture of it and the bolt carrier later if any one cares.

  10. #20
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    Here are the pictures of the Colt buffer and bolt carrier.




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