AR Sponsor
Posted: 3/2/2007 2:52:02 PM EDT
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I installed a A2 buffer tube on my recent build and the tube depresses the buffer detent when it is screwed all the way in. The tube is a brand new take-off from a Bushmaster and the lower is an Eagle Arms. When fully installed, the tube is flush with the top of the receiver. What would be a fix for this? I was thinking I could just file some material from the end of the tube. Any suggestions appreciated. Pic: http://i86.photobucket.com/albums/k108/dp1one2/DCP02185.jpg |
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Yes, just use a file and take a bit off the end of the tube to allow the end of the receiver extension to just kiss the buffer retaining post, and retain it by the tube's edge resting over the outer flat section when tube is installed correctly. Now the scary part, Hopefully the back of the receiver threaded section was just surfaced a tad too much forward, and not that the buffer retaining pin channel was not drilled too far rearwards, with the end result being that the buffer is not pressed rearward off the pin via the back of the carrier when the upper is closed down; causing the buffer to either bend/break the buffer retaining center pin post, or the pin post to have it’s way on the outer edges of the buffer face in the form of denting (number 1 in the below photo).  |
Have you ever noticed that when join the upper to the lower,look very carefully as you slowly join them together. If the BCG just slightly pushes back the buffer then you have a good fit. I think the BCG is what keeps the buffer from actually touching the retaining pin. The pin is only used when you open up the rifle. (I think)
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Bingo, you are correct. It's when the buffer retaining pin is drilled too far back that the back of the carrier doesn't move the buffer off the pin when the action is locked closed. The end result is that the buffer slams the retaining pin each cycle, and when the damage is done. |
| I've got a similar issue with my new 20" Bushmaster HBAR. I am sending it in to Bushmaster. This is the first time I've had any issue with 3 Bushmasters. But it definately has a problem with the buffer hitting th buffer retaining pin. With less than 70 rounds and only a day at the range the buffer is taking a beatting from the buffer retaining pin. When I close the upper on the lower I can clearly see the bolt carrier touch the buffer and move it slightly rearward as the rifle receivers are closed together. Its obvious that either the bolt carrier is too short in length or the buffer retaining pin location is too far back on the lower receiver. I just hope it doesn't take forever to get the situation resolved and that I end up with a 100% relaible and working AR15. |
So what the heck is problem #2 and #3? That's some pretty serious buffer wear. |
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Number 2 and 3 are a combo of edge burs on the back of the carrier, and the buffer not being hard anodized correctly. Light scratches on the center of the buffer are normal to a degree (back of the carrier pushing the buffer back at upper/lower closing), but since the carrier had a wicked bur on the bottom/back U relief channel, this bur was dong a bit of over scrapping on the butter soft buffer face as well. |
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