AR15 Retaining Pin Striking Buffer

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    F

    Fish556

    Member
    Apr 13, 2014
    4
    Baltimore County
    I took a trip to the range today to break in a rifle I recently built and thought I had everything gtg until I broke down my rifle to clean it. Upon inspection, I found that the outer edge of my buffer had been struck by my retaining pin several times. I googled the issue and found multiple answers, but none that seem to apply. This is not a BCG burr issue. I found a suggestion to look at the buffer right as you are closing the upper down and there appears to be a gap as there should be. I checked it against my factory LWRC rifle and the gap appears to be the same.

    The lower (and upper) is from RRA. I googled that they had a problem with out of spec lowers. This lower was purchased many years ago and it COULD be the problem, but seeing the gap between the pin and the buffer seems to say otherwise.

    BCG and Buffer is spikes.

    I did tinker with my adjustable gas block and felt that I left the range with the rifle somewhat overgassed.

    The only idea I have right now is to swap in another BCG/Buffer or both and see if the problem persists. Any suggestions would be much appreciated.
    1zBXDJX

    KymSYdR
     
    smokey

    smokey

    2A TEACHER
    Jan 31, 2008
    31,531
    Google "offset buffer retaining pin". When the upper and lower are closed, the carrier should press the buffer back off of the pin. It shouldn't be hitting the pin at all under normal cycling. Also just double check the tail of the carrier to make sure there aren't sharp burrs near the pin channel.
     
    F

    Fish556

    Member
    Apr 13, 2014
    4
    Baltimore County
    I actually purchased a few of those before I posted this. I am thinking it will fix the issue, but It does look like my BCG is pushing the buffer back enough that the retaining pin isnt touching the buffer, but it is hard for me to tell even with a flashlight. The BCG looks as nice as any BCG I've ever seen so I've pretty much ruled that out. I guess I will have to wait for the offset retaining pin to come.
     
    O

    omegared24

    Ultimate Member
    Dec 23, 2011
    4,747
    Ijamsville, MD
    If the lower is out of spec then not much you can do. They do make a retaining pin that is offset to give some clearance. I'd try another BCG to make sure the carrier isn't too short.

    Tough to tell without gauging.
     
    Decoy

    Decoy

    Ultimate Member
    MDS Supporter
    Mar 2, 2007
    4,929
    Dystopia
    The bolt carrier could be too short, check the length. I think it should be 6.67 or close to that.
     
    paperwork351

    paperwork351

    no error code for stupid
    Mar 7, 2008
    881
    Gaithersburg
    Strange mark pattern. Do you have an accu-wedge installed? Mine is chewed up royally due to a burr. I installed a leither-wise offset and replaced the bolt carrier.
     
    G

    grimnar15

    Ultimate Member
    MDS Supporter
    Jul 21, 2019
    1,645
    Is it me or does the buffer retaining pin look canted left? If that’s the case might I recommend the JP Enterprises silent captured buffer, pricey but it does not require an retaining pin
     
    G

    GolfR

    Ultimate Member
    Oct 20, 2016
    1,324
    Columbia MD
    Are you sure those marks are from the retaining pin? I don't know that I've ever seen a retaining pin strong enough to chip/dent the metal face of the buffer. I would suspect that your retaining pin would be partially mashed if it was hitting that hard.

    Are you sure the marks aren't from the back end of the BCG hitting the edge of the buffer when you swing the upper down? Look at the bottom of your BCG, are there some sharp edges where the buffer channel is cut? Does the BCG contact the edge of the buffer when closing?
     
    John from MD

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,946
    Socialist State of Maryland
    GolfR said:
    Are you sure those marks are from the retaining pin? I don't know that I've ever seen a retaining pin strong enough to chip/dent the metal face of the buffer. I would suspect that your retaining pin would be partially mashed if it was hitting that hard.

    Are you sure the marks aren't from the back end of the BCG hitting the edge of the buffer when you swing the upper down? Look at the bottom of your BCG, are there some sharp edges where the buffer channel is cut? Does the BCG contact the edge of the buffer when closing?
    Click to expand...

    I agree. The buffer is H3 anodized and the pin lower is a hollow tube. No way should it be able to dent the buffer like that without getting seriously deformed.
     
    outrider58

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    50,036
    Usually, the marks are created by the retaining pin groove in the BCG tail. If those marks are indeed caused by the retaining pin, It's only a matter of time before that retainer pin pocket in the lower is blown out. I would measure the length of the bolt carrier. It might be too short.
     
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