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Posted: 9/7/2026 10:12:14 PM EDT
I bought a Ruger Harrier last week, my first AR-15. After some issues and now smooth operation, I'm still finding aluminum shavings in the lower and on the back of the bcg. I think I found where they're coming from though, the bcg appears to be contacting the buffer tube when it cycles. Is there an adjustment I can make or a simple part to replace that would fix this?   I first took it to the range saturday and it barely ran at all. It shot well, but was constantly short cycling or halfway feeding a round and stabbing the bolt into the side of the case. At 100rds I realized it wasn't just a break-in issue and added some thinner oil on and around the bcg. It started cycling correctly and by the end of the 150rd box, it ran 29 rounds without a single failure. The action didn't feel great, kinda gritty, but I chalked that up to break-in and carried on. I shot 150rds of Frontier M193 55gr FMJ. When I took it down for cleaning afterwards, I found the upper and lower to be full of brown lube that had thickened and was incredibly sticky. Where the new oil had gotten into it, it at least behaved like lube. I cleaned everything but the trigger mechanism (not brave enough to take that apart) and lubed it with Rem Oil. While cleaning, I found a bunch of brass debris (surprise :P) and aluminum shavings. I took it to the range again today and fed it 50rds of Fiocchi 55gr FMJ and 150rds of Winchester M193 55gr FMJ. It ran perfectly! Fully cycled every time, locked open every time it ran out, absolutely flawless. When I took it down for cleaning this time, I again found the aluminum shavings, as pictured above. |
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  Take a file and remove the chamfer edge burs on the back of the carrier. Also, make sure to clean up the U bottom slot carrier edge burs at the back of carrier as well. Once completed to remove the carrier burs that are causing harm to the Id of the receiver extension, Birchwood super black to re-color the back of carrier black, and Birchwood aluminum black to touch up the aluminum in the tube. Or, just get Ruger on the phone to send the rifle back, they will do the same, and your out about the same amount of money doing it yourself, verses the shipping cost and time for them to do it instead. Also, pull the B/C out of the back of receiver, and give us a photo of the thickness surround of the ID to OD of the back of upper receiver. It could be that the B/C channel in the upper for the B/C is not centered, and such the case, then rig needs to be sent back to Ruger to have upper receiver out of spec replaced. 
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Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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  I measured the spots you highlighted with a pair of calipers. The left side as pictured is 5.2-5.3mm (0.205-0.209") thick, the right side is 5.3-5.4mm (0.209-0.213") thick. Both are thicker near the top. The id of the upper is 25.36mm (0.998") and the od of the back of the bolt carrier is 23.61mm (0.930"). I now notice that the bcg is not centered in the upper. I can push it around and mostly center it, but it definitely wants to rest here. Something is preventing it from sitting straight. I'm looking into it now, but does anyone have an idea why? |
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Send the unit back to Ruger to clean up the burs on the back side of the carrier/ or just replace, replace the receiver extension, and to replace the upper receiver with one that has been more center drilled drilled correctly so the carrier is centering on the face of the buffer in the receiver extension. The burs you could clean up yourself, but B/C channel in the upper receiver is off enough that it going to keep causing problems. Although for a flat top upper receiver, the needed dimensions are listed for the correct B/C channel location in the upper, https://www.scribd.com/document/50303272/Ar15-A3-style-Upper-receiver-blueprints |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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