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Posted: 10/31/2010 2:52:07 PM EDT
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A buddy of mine put together an AR with a Noveske blem lower(gave it to him as my contribution to his project) that I recieved directly from Noveske. Also used was an LMT 16" carbine upper, a Stag LPK, and a BCM buffer tube/buffer/and stock. All parts were purchased new. It seems that, after 200 or so rounds, the face of the buffer is getting dinged up by the buffer retention pin. The dinging is very obvious and completely covers the outside face of the buffer.In other words, it appears that the buffer is rotating as the rifle cycles...causing the buffer retaining pin to ding up the complete outer lip of the buffer face.
Any ideas what might be causing this? It seems that I saw a post about a similar problem here months ago, my search-fu is weak and I'm having a hard time finding that thread...I'd definitely like to know the problem wound up being. At this point I can only think that it might be the BCG is out of spec in length(allowing the buffer to slam into the pin) or perhaps a misthreaded journal for the tube to thread into. Perhaps an incorrectly made buffer tube? What sayeth the hive? And, yes, I know..pics would help. I wasn't in any way able to snap some pics when I buddy showed me the rifle..I'll see if I can get pics soon. Thanks!! -D2V |
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It's most likely not the buffer retaining pin, but rather a burr on the rear of the bolt carrier, pretty common.
http://www.weaponevolution.com/forum/showthread.php?1744-BOLT-CARRIER-LAPPING-DEBURRING-PROCEDURE |
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If you are talking about a ring on the face of the buffer, it's fairly common, IIRC. It's caused by a bur on the end of the BCG.
There is a post here about stoning the end of the BCG. Fairly normal, all my AR's have it in one degree on another. I'll post pics later. |
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The spring will slowly turn no matter what. If you want to demonstrate the principle yourself, here's what you do: Remove the spring, immobilize one end with a hand. Compress the spring with your other hand, look at the end while it's compressed. It's not a lot, but it'll slowly turn inside the receiver extension. |
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If they are dents around the very outside edge of the buffer it may be the retaining pin hitting. If they are in from the outside edge slightly it may just be a burr on the rear of the carrier, maybe at the notch that rides over the retainer pin.
Not a whole lot to do if it is actually hitting the retainer pin. Could check the carrier or swap upper to see if it helps but I would doubt it would. Would be nice to have an offset tipped pin but never seen one. You could used a notch in the buffer tube to keep the pin from rotating side to side. |
Does it look like this?
This was caused by the aforementioned burr on the end of the BCG. You can see where it scratched the buffer as I opened and closed the upper, too. As I shot, it caused "chatter marks" in a circular pattern as the buffer rotated. I used a fine file to dress up the end of the BCG and fixed it. (This was on a Colt 6920, btw. ;) ) . . |
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Quoted:
Does it look like this? http://www.mrossnet.com/Buffer.jpg This was caused by the aforementioned burr on the end of the BCG. You can see where it scratched the buffer as I opened and closed the upper, too. As I shot, it caused "chatter marks" in a circular pattern as the buffer rotated. I used a fine file to dress up the end of the BCG and fixed it. (This was on a Colt 6920, btw. ;) ) . . It looks similar, but much worse. I'll see if I can snap some pics and post an update in a few days. Thanks for the head's up guys...I may have him drop off the BCG so I can do some work on it. -D2V |
| To rule out the buffer retaining pin just scissor the gun open, leaving in the takedown pin, and then slowly bring the upper back down onto the lower. If you can see that the back of the bolt carrier nudges the buffer back off of the retaining pin, you're gtg. |
| Its the back of your carrier....trust us. It wont really hurt anything, but is very easy to fix like already said. If it somehow is your retaining pin then you need to get the rifle looked at and eventually that little tip will break of can cause all kinds of problems. |
| The buffer retaining pin does nothing and touches nothing until you open the action, which allows the buffer to move forward under spring pressure. It hits the BRP and stops, which allows you to service the weapon without parts and springs shooting out all over the place. The marks you are seeing on the buffer come from the back end of the bolt carrier like everyone else has said. This happens frequently on 'put-togethers' when the builder doesn't know to smooth the edges on the rear of the carrier. |
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The buffer retaining pin does nothing and touches nothing until you open the action, which allows the buffer to move forward under spring pressure. It hits the BRP and stops, which allows you to service the weapon without parts and springs shooting out all over the place. The marks you are seeing on the buffer come from the back end of the bolt carrier like everyone else has said. This happens frequently on 'put-togethers' when the builder doesn't know to smooth the edges on the rear of the carrier. This happens to some extent on all my rifles, not just my "put togethers." I have never bothered trying to de-burr the bolt carrier because I really don't see the buffer scratching as an issue. |
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The buffer retaining pin does nothing and touches nothing until you open the action, which allows the buffer to move forward under spring pressure. It hits the BRP and stops, which allows you to service the weapon without parts and springs shooting out all over the place. The marks you are seeing on the buffer come from the back end of the bolt carrier like everyone else has said. This happens frequently on 'put-togethers' when the builder doesn't know to smooth the edges on the rear of the carrier. This happens to some extent on all my rifles, not just my "put togethers." I have never bothered trying to de-burr the bolt carrier because I really don't see the buffer scratching as an issue. I didn't either until I bought a Colt and it didn't happen. I found out why it happened on my put-togethers and fixed it. |
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Quoted:
Quoted:
Quoted:
The buffer retaining pin does nothing and touches nothing until you open the action, which allows the buffer to move forward under spring pressure. It hits the BRP and stops, which allows you to service the weapon without parts and springs shooting out all over the place. The marks you are seeing on the buffer come from the back end of the bolt carrier like everyone else has said. This happens frequently on 'put-togethers' when the builder doesn't know to smooth the edges on the rear of the carrier. This happens to some extent on all my rifles, not just my "put togethers." I have never bothered trying to de-burr the bolt carrier because I really don't see the buffer scratching as an issue. I didn't either until I bought a Colt and it didn't happen. I found out why it happened on my put-togethers and fixed it. What I'm saying is that my Colts, BCMs, etc do it as well. These are not "put togethers," but factory rifles. |
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