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Decimator/DecimatAR with OEM barrel (forum.guncadindex.com)
submitted 1 month ago by hogleg@forum.guncadindex.com to c/help@forum.guncadindex.com
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I have been incapable of finishing a decimator build with an OEM barrel; 2 different OEM barrels as a matter of fact.

I've reprinted the upper twice (once because I wasn't sure if I just really messed up the print, once for stripping barrel nut threads) and I've reprinted the barrel nut 3-4 times at this point.

I started this build just before fosscad was nuked, and since the Ark is back up (https://forum.guncadindex.com/c/ark@fosscad.io), I was able to see that there are threads where others have had this issue.

Has anyone overcome this issue personally? The build looks great and I love the AR fcg but I'm hitting a wall here. Should I just drill and pin the barrel nut with a couple of set screws?

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[-] hogleg@forum.guncadindex.com 2 points 3 weeks ago

I wanted to make sure I updated this for anyone following down the road. I didn't realize what the problem was until I printed the actual R2 Galileo barrel nut and compared; the hole for the barrel on the R2 was much wider than the Decimator v3. I dropped a 23.2mm negative cylinder into the center of the Dv3 barrel nut and it resolved the problem. I've not got any experience with printed barrels to compare, but I imagine their OD is narrower than the widest portion of the factory barrels I was working with.

[-] notsuspekt@forum.guncadindex.com 0 points 1 month ago* (last edited 1 month ago)

Join the DD rocketchat and talk to Decimal yourself, he's an awesome guy.

Before doing that, calibrate your printer. The upper/barrel/nut interface depends on some pretty narrow tolerances.

[-] hogleg@forum.guncadindex.com 0 points 1 month ago

Thanks! I'm dialed in on flow ratio, pressure advance, e-step, as far as I can tell and I've got several other successful prints. None of them using printed threads like this, though. I'll see if I can bend his ear about it.

[-] notsuspekt@forum.guncadindex.com 0 points 1 month ago

If I recall correctly, he oriented the barrel nut super weird, with the bore facing sideways. I did mine vertical and it threaded on fine but he had a good reason for that orientation.

Have you done dimensional calibration, like a calilantern?

[-] hogleg@forum.guncadindex.com 0 points 1 month ago

Yeah, I ran into the same thing with the orientation; got farther after orienting it vertically, but like you said, he had a reason for the original orientation.

And I have not done that; I've never even heard of the calilantern. I will for sure give that a go. Thanks!

[-] notsuspekt@forum.guncadindex.com 0 points 1 month ago

It helps a lot with threads, and under/over extrusion. If you need the files DM me, you're not supposed to share them cause OP has cancer and he sells them.

[-] hogleg@forum.guncadindex.com 1 points 3 weeks ago

Hey, thanks again for the assistance! I didn't get back to this for awhile; life things. I left an update up at the top for anyone in the future.

this post was submitted on 12 Oct 2025
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