this post was submitted on 05 Nov 2025
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Howdy all,

Quick question on the BiPoly, as I've only built 80% AR builds up to this point. It doesn't appear it takes a standard buffer tube; is there a way to run a traditional stock on the BiPoly setup, or does it have to be one of the printed stocks that come with the file pack? Obviously it's not threaded for a buffer tube, but it would be great to be able to run a standard multi position AR stock on it; I haven't been super happy with the printable 3 position.

Thanks

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[–] notsuspekt 7 points 1 month ago (5 children)

The bipoly makes no sacrifices on strength, that fixed stock is king as the buffer tower is traditionally a weak point. If you want to run a buffer tube and a collapsible stock, something like the Defiance or SL-15 are more appropriate.

That said, don't sleep on the bipoly. It's 100% my favorite lower and worth building one for yourself.

[–] literallyjustmax 2 points 1 month ago (4 children)

I guess I'm missing something in the build; I printed the PRS style stock, but how does the buffer get held into it? I don't see a set screw point for capturing the buffer and spring inside the stock assembly.

[–] notsuspekt 2 points 1 month ago (3 children)

That's a great question, the bipoly's creator determined that including a hole for a buffer detent would lower strength so there is none, you hold it back while you install the upper.

Like I said, it makes no sacrifices on strength. My pla version is well over a year old with thousands of rounds through it and I'm not the only person with these results. I think he was on a good path with this one.

[–] literallyjustmax 2 points 1 month ago (1 children)

I printed the lower in PA6-CF, guess I’ll have to give it a shot (pun intended). Probably will end up Form-1’d with a 10.5” upper in .300 BLK. Thanks for the tips, I’ll see how she shoots :)

[–] notsuspekt 1 points 1 month ago

You're gonna love it. I'm gearing up to print it in one piece, no seam like a Monopoly.

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