AR10 Buffer Spring Failure

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  • j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    A friend stopped over this evening for me to look at his AR10. He said he was at the range and it started failing just about every way an AR can fail. So we took it apart and found the buffer spring had broken off the last 3 or so twists in the spring. I found a few pieces of the broken spring in the buffer tube, but there appears to be more missing than we can't account for. Where could it go. I'm thinking there are more than 2 twists of spring still unaccounted for. There was nothing else in the buffer tube, nothing in the lower, the upper looks clean.

    Where did it go?

    Secondly, has anyone heard of a buffer spring breaking like this? I know it could have just been a bad spring, but anything else? I don't believe the rifle is over pressured because I've watched him shoot it in the past and the rounds dropped within 8 feet, all in about a 2 ft area.

    Interesting to say the least!
     

    iH8DemLibz

    When All Else Fails.
    Apr 1, 2013
    25,396
    Libtardistan
    What are the chances of having more spring than space in the buffer tube?

    The spring could have cracked because the coils were beating against each other.
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    Sounds like the spring was compressing to solid height which will cause spring breakage. This often happens by using a buffer spring that has coils that are too fat or is too long for the buffer that is used.

    Believe it or not it's quite common, especially in large frame .308 type AR die to parts variations.

    I pass around spring examples in my classes that have coils that are too fat which means the spring compresses to solid height before the buffer pad can make contact with the rear of the buffer tube.


    Have him put in a tubbs flat wire spring. They can't go to solid height.
     
    Last edited:

    j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    What are the chances of having more spring than space in the buffer tube?

    The spring could have cracked because the coils were beating against each other.

    It's a factory built rifle. I'm not saying it can't be, but I don't think so. But who knows?
     

    j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    Sounds like the spring was compressing to solid height which will cause spring breakage. This often happens by using a buffer spring that has coils that are too fat or is too long for the buffer that is used.

    Believe it or not it's quite common, especially in large frame .308 type AR die to parts variations.

    I pass around spring examples in my classes that have coils that are too fat which means the spring compresses to solid height before the buffer pad can make contact with the rear of the buffer tube.


    Have him put in a tubbs flat wire spring. They can't go to solid height.


    The spring looks just like my old one. After I installed the Tubbs Spring, I kept my old spring. I installed my old spring into his rifle and I guess we'll see what happens. His broken spring and my old spring looked pretty close to the same. I didn't mic them, but by eyeball, they looked the same except his was about an inch shorter.

    As important as the broken spring itself, I'm curious where the broken parts went to. Like I said, I've got maybe 3/4 of a complete twist in 2 different pieces, but there's probably another 2 full twists of the spring missing. Where could that have gone?
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    The spring looks just like my old one. After I installed the Tubbs Spring, I kept my old spring. I installed my old spring into his rifle and I guess we'll see what happens. His broken spring and my old spring looked pretty close to the same. I didn't mic them, but by eyeball, they looked the same except his was about an inch shorter.

    As important as the broken spring itself, I'm curious where the broken parts went to. Like I said, I've got maybe 3/4 of a complete twist in 2 different pieces, but there's probably another 2 full twists of the spring missing. Where could that have gone?


    Hard to say where the broken pieces went.

    A mic is needed to check spring wire diameter or the whole spring is needed to check it's height when compressed over the buffer. You can't measure solid height since spring bits are missing.

    Problem is some companies use 5.56 length springs for .308 buffers and most .308 buffers are shorter than their 5.56 variants. This means the standard music wire type round spring goes to solid height and does not let the buffer pad do it's job. Stout recoil, broken springs, and reliability problems often are the result. It's worse on variants with a large gas port and .308 ammo which can be hotter than 7.62 NATO.
     

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