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Posted: 2/28/2026 6:08:26 PM EDT
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What the heck would cause this, looks like the back of the carrier is hitting the buffer retaining pin?????. So the pin is out of spec or the carrier is? This is a new build on an old 2008 stag lower, brovo upper, the BCG has a “A” on the left side, Aero? First time in more than 30 builds. The LPK IS STAG. |
| So how the heck could this even happen? The carrier is pushing the buffer a bit, I have .022gap. I mean when the receivers are closed, the bolt carrier is pushing on the buffer. There is no rear word movement for the back of the carrier at the bottom to hit the pin.🤷♂️ |
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I used feeler gauges to measure the gap at the rear of the upper and lower receiver when the takedown pins were out. I should also mention there is wear on the inside edge of the rear just above those chips. I can’t figure out what it’s hitting. I meant the rear of the bolt carrier is depressing the buffer by 20,000s of an inch when the receivers are closed that damage looks like it impacted something during recoil, but there’s nothing for that carrier to hit. Needless to say, I should probably not use this carrier ever again🤷♂️ |
| No idea looks normal. The retainer pin is not bent to one side or made off center slightly where if it is rotated the top of the pin would make some larger than its diameter circle? I don't see how it could be the pin there would have to be more than one thing wrong for the pin to catch or rub near two corners. |
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That is really weird. The carrier essentially has to be rolling all the way clockwise or counter clockwise in the channel on the ignition cycle, never centered. The buffer retaining pin is not bent and MAYBE is a little rounded but otherwise undamaged. I'd measure the retaining pin height and see how it specs. There's really nothing else that fits. |
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I took out some extra colt, toolcraft, and microbest BCG and measured the depth of that channel, they all measured about 2.38-2.44mm deep, the carrier in the photo measured 2.18mm deep. I don’t think it was cut deep enough, it’s a ANDERSON BCG, it somehow got mixed up with all my other spare parts. Not sure when I picked it up. I assumed it was a tool craft but nitrate. Either way it’s going in the trash as when I compared the channel with the other bolt carriers it definitely appeared to be cut shallow and that may be how those two chips at the back of the carrier happened. I still can’t figure that out because the carrier should be pushing the buffer into the extension, but I also did notice when I put a tool craft bolt carrier group in that the receivers closed more easily and I could feel a little more gap at the rear so perhaps that was what was wrong. |
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WI, USA
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C'mon man, RECYCLE! Start a steel scrap bin. It pays, (not much), but requires, like, no work. The aluminum and copper/brass bins pay better. Besides, a healthy metal recycling industry improves the reliability of our domestic metal supply, which has been a subject of presidential interest as it relates to national security. (Moreso steel and copper than aluminum, from what I've read, but I've only paid so much attention.) In short, metal recycling: easy, profitable (and therefore quintessentially American), promotes national security (and therefore patriotic), reduce landfills fill rates (making them more efficient), and it makes psychics see glowing American flags if they try to read your aura. |
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I think the print depth range for the slot converts to around 2.41mm - 2.66mm. Still odd with the pin width, slot width, and angle cuts that are supposed to be on top the pin like the prints show it could mark that far apart. Like a poster mentioned maybe the carrier was moving around some too. I had always thought the carrier would kind of stayed more aligned during use, but I should have known better than that just by looking at the wear patterns on old buffer faces. |
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Originally Posted By titan7: Ok , I’m green, I pulled them out of the trash. I wish I trusted any part of the BCG to keep, but after seeing some lugs getting sheared on a Anderson bolt at 150 rds, I’m thinking these are a liability. Keep it as a spare. Use the carrier with a BEV block. Gift it. Sell it with full disclosure . No sense in shit canning it. |
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