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Posted: 3/10/2013 7:20:41 PM EDT
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Purchased and received my Black Rifle Arms AR-15 16" 5.56x45 Low Profile Carbine Piston Upper and promptly attached it to my newly built multi-cal lower which I built from all new parts for this upper. The upper is a nice piece for what I paid and I have no complaints what-so-ever.
I took the rifle out today for the first time to the range. I fired several different loads through it, (including some steel cased just for giggles), amounting to ~100 rounds; all without any fire, feed, or extraction issues. However upon tearing down the rifle when I got home for inspection I found a very curious groove in the buffer tube, (see attached images). The buffer tube is a standard mil-spec 6-position. I can’t really put my finger on this one. Rather than the obvious signs of carrier tilt, (which there isn’t any), it looks as though something “pressed” or “rolled” a grove into the buffer tube to the point of a stress crack. It is really odd to me that there are no scratches in the anodizing of the tube here, just an indentation. I’m new to the AR platform so I don’t know; is it possible something got in-between the bolt carrier and buffer tube when it cycled causing this? It’s odd that the damage is directly in-line with the buffer retainer and on the weakest part of the buffer tube. It’s even stranger that there is the groove cut in the bolt carrier buffer and machined into the bolt carrier that I think would allow anything small to pass through and not get pushed into the buffer tube…especially at the spot the damage is. As you can see in the attached images, neither the bolt-carrier buffer nor the bolt carrier show any signs of wear or damage. The action spring and buffer look good too. Have you guys ever seen this sort of thing before? I’m ordering a new buffer tube but on the off chance you all see something I don’t, I would hate to put it all back together to only see the same results after the next hundred rounds. I think I would of felt better if something just fell out when I took it all apart. At least then I would know what was what. I don’t think all of this matters much but I’m using a Sprinco “red” spring and an ST-T2 buffer. The only modifications/changes I made to the factory Black Rifle Arms Upper upper is I changed out the bolt to a Kies NiBor unit and installed a McFarland gas ring, (just because), and a BCM extra strength extractor spring. I also put in a POF roller cam pin and I’m using a BCM ambi-charging handle and a Vortex flash suppressor. http://www.nucmotorsports.com/pics/263.JPG http://www.nucmotorsports.com/pics/264.JPG http://www.nucmotorsports.com/pics/265.JPG http://www.nucmotorsports.com/pics/266.JPG http://www.nucmotorsports.com/pics/267.JPG http://www.nucmotorsports.com/pics/268.JPG |
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Under sized receiver threads squeezing the tube together when it was screwed in? How difficult was it to install the receiver extension? Kinda looks that way since the indentation isn't straight like one would assume would happen if there was something dragging or catching in there. Haven't seen anything quite like it. |
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Looks like just marks left over from an extrusion process of manufacturing the tube. Blurry pics make it hard to tell exactly what I'm looking at. That's a theory except the "damage" wasn't there when I originally assembled the rifle. I'm one of those OCD guys and I certainly would have noticed it. |
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It actually looks more like it buckled rather than a gouge. When something squished it, the path of least resistance was the thinner unthreaded portion. I agree. If the damage was caused by the mere act of firing the upper there would be some evidence of abrasion. The pics' don't appear to show any. The pic quality may be hiding any other evidence from us. Was there any metal filing or other debris in the tube, lower or upper in the area of the BCG tail. I understand you feel you would have noticed this prior due to your attention to detail, but things have been missed by others who have just as keen an eye as us OCD types. Please keep us informed as you discover anything else. Additional: The more I look at your tube the more I'm thinking its a result of the manufactuering process. The finish is still on from the looks of it. I can't imagine any other culprit. Especially since there is no other stress on the tube other than the BCG, buffer, and spring. Just keep your spare tube and shoot the current tube. Just keep on checking (although I don't think you'll find any other weird signs of probable problems. |
| I know you said you're ordering a replacement, but if you haven't ordered yet get a BCM Milspec receiver extension and don't look back. |
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I know you said you're ordering a replacement, but if you haven't ordered yet get a BCM Milspec receiver extension and don't look back. The one pictured is not milspec size, so his current stock would not fit on this replacement from BCM. |
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I know you said you're ordering a replacement, but if you haven't ordered yet get a BCM Milspec receiver extension and don't look back. The one pictured is not milspec size, so his current stock would not fit on this replacement from BCM. Good point, I looked for text saying what he currently had and didn't find it, but looking at that picture it appears he has a commercial spec receiver extension. So this topic should probably be "sub-milspec parts suck." OP, get the correct milspec receiver extension and then get a stock to go with it. Sub-milspec parts suck. |
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I know you said you're ordering a replacement, but if you haven't ordered yet get a BCM Milspec receiver extension and don't look back. The one pictured is not milspec size, so his current stock would not fit on this replacement from BCM. OK then this and don't look back. BCM M4 MilSpec Stock Assembly |
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I know you said you're ordering a replacement, but if you haven't ordered yet get a BCM Milspec receiver extension and don't look back. The one pictured is not milspec size, so his current stock would not fit on this replacement from BCM. OK then this and don't look back. BCM M4 MilSpec Stock Assembly His buffer, spring, castle nut, and end plate should work fine; they're the same between a commercial and milspec receiver extension. Unless of course the roll pin is coming out of his buffer and is gouging the tube. Or if he used one of those garbage buffers that doesn't have a roll pin and is going to fall apart in a few more rounds... Either way, the lesson here is probably to use quality parts. And yes, he'll need a new stock to match the new tube. |
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