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Hopefully others will find this helpful if they run into the same issue.

So I recently just finished my first ar pistol in 9mm. I've always loved and wanted the mp5 but they, and their 9mm variants are usually far too expensive for my taste, and the .22s, though fun, just don't have the umph I'd like it too have and the one I did have was way too unreliable to ever really enjoy.

Anyways, for my build I decided to use the RRA pistol buffer tube which would be mated to my new frontier armory glock 9mm lower. And for the end plate I used the Odin works with the dual sling loops. When mocking up the lower I found that the buffer tube was tight before it was able to engage/hold the buffer retaining pin. A small annoyance that could be left alone, sure, but over time i know a day would come when I would forget the pin isn't there and I would open up the pistol and have a 7.5oz buffer headed toward my face.

IMG_1859.JPG IMG_1860.JPG

As you can see the Odin works end plate is rather thick, but even with a regular end plate it would still barely be over the pin, not enough for me to trust it. Plus I really liked and wanted to use the Odin works plate.

I had a cheap out of spec carbine tube laying around and figured I could cut off just the end with enough thread to hold in the pin and still fit between the buffer tube and allow the upper to close still. So I took the old buffer to a band saw and cut off the end with about two rows of thread giving me enough to sand down and adjust as necessary.

IMG_1862.JPG
IMG_1864.JPG IMG_1865.JPG

Once in place I installed the tube to see where I was. First fitment the buffer tube couldn't thread in quite all the way before hitting the ring. Since the pin was already sitting pretty deep into the retainer, I thought it would be better to sand out the retaining pocket on the ring a little deeper and spin the ring out one more rotation, then sand the front of the ring so it would sit flush with the ear of the lower and allow the upper to pin in.

Their may have been easier fixes for this but hey it worked! Cutting, fitting and sanding maybe took me 30min to get it to fit perfect.

The end result!

IMG_1867.JPG
 
Huh, I've never had a pistol or carbine tube not thread in with plenty of threads left to spare. I read the post several times....so what was the original problem? Is that pistol tube not threaded far back enough?
 
I think the issue was this tube wasn't meant to be used with a castle nut, it just threads straight in. So while it threads in just as much as a normal buffer tube would It doesn't have the ears that extend out like a normal buffer tube to engage the pin, since you can't time it and tighten it with the castle nut, it's cut flush. That's my theory anyway.

I've seen this on a couple other forums with similar style buffer tubes where they only half maybe half a thread holding in the pin and they've sometimes come out.
 
I think the issue was this tube wasn't meant to be used with a castle nut, it just threads straight in. So while it threads in just as much as a normal buffer tube would It doesn't have the ears that extend out like a normal buffer tube to engage the pin, since you can't time it and tighten it with the castle nut, it's cut flush. That's my theory anyway.

I've seen this on a couple other forums with similar style buffer tubes where they only half maybe half a thread holding in the pin and they've sometimes come out.
PSA makes pistol buffer tubes that do not require a castle nut. Pretty slick.
 
If you need one let me know, I have an extra new in package that I would sell for $30 shipped

I appreciate that, I'll have to see how I like the rra one over time I just finished the build and took it out this morning for the first time, runs good so far. Wanted to make sure it worked before I posted a 'fix' lol.
IMG_1869.JPG
 
Nice fix. I had a tube with a similar issue and went about the fix another way, by threading the detent hole and putting a set screw in it and doing away with the back plate all together. I then blue loctite'ed the RE in after filing the end of the threads down to the proper depth to hold the buffer retainer pin.

It was not a pistol tube but a cheap Chinese knock off of a light weight Battle arms Sabertube type stock. I was just trying to get the parts put together to trade it in and all I cared about was that it functioned. It did. Anyone who knew anything about AR's though would have looked at it and said "What the hell?" :D
 
Nice fix. I had a tube with a similar issue and went about the fix another way, by threading the detent hole and putting a set screw in it and doing away with the back plate all together. I then blue loctite'ed the RE in after filing the end of the threads down to the proper depth to hold the buffer retainer pin.

It was not a pistol tube but a cheap Chinese knock off of a light weight Battle arms Sabertube type stock. I was just trying to get the parts put together to trade it in and all I cared about was that it functioned. It did. Anyone who knew anything about AR's though would have looked at it and said "What the hell?" :D

Now that I like, a threaded retaining pin sounds like a good idea
 

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