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Posted: 11/1/2016 9:05:02 AM EDT
| So I recently bought a custom Matrix Aerospace 7.62 AR10. I took it to the range where it performed very well until the trigger seized and the gun became inert. I remove the takedown pin and immediately the buffer assembly shot forward. The buffer detent had been completely shattered and found its way under the fire control group. I was stunned and didn't know what the problem was so I took the lower parts kit out of the lower and removed the fragments of the detent. The fire control group worked perfectly so I went ahead and ordered another detent from ArmaLite. I put the buffer detent back in the lower when I received it only to find that the real problem was that the buffer looked to have been trimmed. It had small spots around the buffer which allowed it to bypass the detent. I was amazed I didn't know if it was an act of sabotage or just the way the buffer was manufactured. Is this normal in AR10s? I will provide pics when i figure out how to upload one. |
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The purpose of the buffer retaining detent is to keep the buffer inside the receiver extension (buffer tube) when you hinge open the upper from the lower. When the upper and lower are fastened together (rifle is closed up), the back of the bolt carrier pushes the buffer slightly rearward so the buffer then has no contact with the buffer retaining detent. If you buffer retaining detent is coming out of the hole in the lower receiver, then you may need to tighten the receiver extension (buffer tube) in a little further on a collapsible stock so that the receiver extension (buffer tube) covers approximately the back 1/3 of the buffer retaining detent. If you have a fixed stock, then the receiver extension (buffer tube) needs to be tightened until its shoulder stops and cinches tight against the back of the lower receiver, and if the buffer retaining detent can still slip past the receiver extension (buffer tube), then you may have an out of spec or damaged lower receiver hole where the detent is retained.
CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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Fixed OPs picture: 
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| The buffer tube is very tight against the detent. Its the buffer i think is out of spec. Ill provide a pic below. There are 3 notches on the buffer and after so many rounds the buffer itself rotates due to the bolt hitting it. Then once its rotated to where the notch is the buffer and buffer spring by pass the detent. http://s44.photobucket.com/user/Noah_Bridges/media/Mobile%20Uploads/14780144599881023942887_zpsax0bqho8.jpg.html |
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Quoted:
The buffer tube is very tight against the detent. Its the buffer i think is out of spec. Ill provide a pic below. There are 3 notches on the buffer and after so many rounds the buffer itself rotates due to the bolt hitting it. Then once its rotated to where the notch is the buffer and buffer spring by pass the detent. http://s44.photobucket.com/user/Noah_Bridges/media/Mobile%20Uploads/14780144599881023942887_zpsax0bqho8.jpg.html Notches are completely normal. No idea what your issue is but that buffer looks ok to me. |
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Hello,
In my humble opinion.After seeing your picture,your problem is that your BRD (Buffer Retainer Detent) and buffer tube are not installed properly.My first Red Flag appeared when you said it was a "custom" build.Anyway,when the buffer tube is installed on a fixed or collapsible stock clearance MUST be maintained between the buffer tube and,the BRD Tit. That is the small portrussion app.1/8"H x1/8"D that is on top of the detent body (the portion that retains the spring).The end of the buffer tube should only come in contact with the FLAT surface of the BRD by about 1/32".That is app. 1/2 the distance between the edge of the BRD and the BASE of the TIT.The BRD is app.1/4"D,the Tit is app. 1/8"H x1/8"D.If,you screw the tube up against the Tit,it will bind.Therefore,making it difficult to depress when you want to remove the buffer/spring for any reason.Also,in the photo you provided your TIT ,or the majority of it is missing.It was either broke or altered by someone who doesn't know what they are doing.Compare that one with your new one and you will clearly see what I'm talking about.By the way,buffer's will rotate and the three relief cut's are from the factory.So,in ending try it my way and watch what happen's. |
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The problem is your buffer tube is screwed in one turn too far, or it needs a small u notch cut into it, so the buffer retainer can sit higher. Right now, it is being retained too low, so the notches are free to bypass it as was stated. The buffer rotates during operation.
At first, I thought maybe the wrong spring was installed under the buffer retainer, but I think it is the tube as I already described. It may still be the wrong spring, but try backing out the tube so the retainer body is sitting about flush with the threads, not with the tit barely sticking up onto the buffer face. If you back off the buffer tube and the retainer still sits very low, you need to get the proper spring that is supposed to be under the retainer. |
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