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Started By
Message
Buffer tube won't screw into AR lower receiver
Posted on 9/28/21 at 11:39 am
Posted on 9/28/21 at 11:39 am
I ordered an SBA3 brace a few months ago on sale. It came with a buffer tube.
Just ordered a PSA glock AR complete lower but it came with a fin brace and I want to swap out the nicer brace onto it. Well the tube that came on it is a perfect cylinder and also is a little fatter at the end so it won't accept a regular AR sized stock/brace so I'm going to swap out the buffer tube for the tube that came with my SBA3 brace.
Well it won't thread on. I can turn it once or twice then it seizes up. The threads on both male/female parts are good. The fatter buffer tube came right off and the castle nut threads right onto the new tube with no resistance or locking. But the receiver just won't accept the new buffer tube. Anybody got any help? I really don't want to stick with the fin brace and I feel like returning a lower will be a nightmare.
ETA: Fixed the issue. It was tolerance stacking. That particular buffer tube and receiver combo was a no go. But I tried a couple different tubes and one screwed in. All the tubes worked on other receivers so I'm imagining the new receiver was a little more out of spec than the new tube and they both just were too much for each other. Glad that was able to sort itself out without needing to buy another several tubes potentially or a new receiver.
Just ordered a PSA glock AR complete lower but it came with a fin brace and I want to swap out the nicer brace onto it. Well the tube that came on it is a perfect cylinder and also is a little fatter at the end so it won't accept a regular AR sized stock/brace so I'm going to swap out the buffer tube for the tube that came with my SBA3 brace.
Well it won't thread on. I can turn it once or twice then it seizes up. The threads on both male/female parts are good. The fatter buffer tube came right off and the castle nut threads right onto the new tube with no resistance or locking. But the receiver just won't accept the new buffer tube. Anybody got any help? I really don't want to stick with the fin brace and I feel like returning a lower will be a nightmare.
ETA: Fixed the issue. It was tolerance stacking. That particular buffer tube and receiver combo was a no go. But I tried a couple different tubes and one screwed in. All the tubes worked on other receivers so I'm imagining the new receiver was a little more out of spec than the new tube and they both just were too much for each other. Glad that was able to sort itself out without needing to buy another several tubes potentially or a new receiver.
This post was edited on 9/28/21 at 3:39 pm
3
Posted on 9/28/21 at 12:12 pm to jlovel7
Ya, I dont know what I was thinking.
But i would still try a different buffer tube.
But i would still try a different buffer tube.
This post was edited on 9/28/21 at 12:37 pm
Posted on 9/28/21 at 12:20 pm to Shexter
Funny, I've never seen a lower specify commercial vs mil-spec.
Posted on 9/28/21 at 12:29 pm to bbvdd
quote:
I've never seen a lower specify commercial vs mil-spec.
Oh,.... that pic has nothing to do with the original post...... I was just, uh, posting a random photo..... Yup.......
Posted on 9/28/21 at 12:30 pm to Shexter
quote:
Oh,.... that pic has nothing to do with the original post...... I was just, uh, posting a random photo..... Yup.......
Posted on 9/28/21 at 12:33 pm to bbvdd
Maybe this is your issue. From Calguns:
https://www.calguns.net/calgunforum/showthread.php?t=683184
quote:
I received a palmetto State moe lower build kit this week and was building the stock together. The buffer tube gets about a half turn and then will not screw in any more. I tried it on 3 different lowers with the same results.
I have another moe kit from psa and that buffer tube screws in no prob as did the pistol buffer from my ar pistol.
quote:
I had that with a PWS buffer.. it was just a bit "out of spec".. Nothing to do but send it back..
https://www.calguns.net/calgunforum/showthread.php?t=683184
Posted on 9/28/21 at 12:35 pm to jlovel7
The castle nut to the old tube screws onto the SBA3?
Do you have another lower you can try the SBA3 with? If the castle nut that came off the old tube screws on the SBA3, I may lean toward you getting it cross threaded somehow.
I'm not sure if the PSA AR9 has a different sized thread. May call PSA and ask.
Do you have another lower you can try the SBA3 with? If the castle nut that came off the old tube screws on the SBA3, I may lean toward you getting it cross threaded somehow.
I'm not sure if the PSA AR9 has a different sized thread. May call PSA and ask.
Posted on 9/28/21 at 12:46 pm to bbvdd
The buffer tube that won't screw into the new lower will screw in just fine in another lower. I'm going to try and see if I can get a buffer tube from other builds to work and do some mixing and matching.
ETA: My rifle buffer tube for another build that I had laying around screwed in just fine to the new lower. So I'm thinking this is a case of "tolerance stacking" where it just happens that the tolerances of this particular buffer tube and this particular receiver don't like each other.
ETA: My rifle buffer tube for another build that I had laying around screwed in just fine to the new lower. So I'm thinking this is a case of "tolerance stacking" where it just happens that the tolerances of this particular buffer tube and this particular receiver don't like each other.
This post was edited on 9/28/21 at 12:48 pm
Posted on 9/28/21 at 12:47 pm to bbvdd
Yeah PSA is pretty good fixing their errors. They will get back to your withing a business day if your explain the problem well and maybe send pictures in email. I would call get a name and email then email. They will be able to explain or fix
Posted on 9/28/21 at 1:05 pm to jlovel7
quote:
"tolerance stacking" where it just happens that the tolerances of this particular buffer tube and this particular receiver don't like each other.
I did see where the peaks of the threads on the buffer tube may be too tall for the PSA after my other post. May try to hit them with sandpaper to knock the peaks down a couple thou.
Posted on 9/28/21 at 2:15 pm to bbvdd
quote:
I did see where the peaks of the threads on the buffer tube may be too tall for the PSA after my other post. May try to hit them with sandpaper to knock the peaks down a couple thou.
I had this issue with a savage style prefit barrel and barrel nut. The nuts threads were way sharper and deeeper than the barrels. Had to sand them down a little bit, but it eventually fit.
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