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Discussion Starter · #1 ·
Sure hope I'm missing something with the installation process. I have a CMMG barrel I'm trying to install, along with their 1/2x28mm thread adapter.

Everything going smoothly during testing until I try and tighten everything down. Even just finger tightening, the thread adapter bottoms out on the receiver, so that it's no longer "floating" or sprung. I've seen one case mentioned on the internet elsewhere and they concluded the barrel was out of spec in that case.

Called CMMG and was greeted by a robot telling me they just don't answer their phones anymore, and they don't respond to voicemails either. I did send them an email and haven't heard anything. Hoping someone here can help.
 

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Is the barrel return spring in place?
 

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Discussion Starter · #3 ·
Yes sir, assuming there's no more correct way to install it that putting in the barrel cavity and tightening the barrel into the thread adapter.
 

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No, that's it. Do you have a flash hider you can try in place of the adapter? It does sound like either the barrel or adapter may be out of spec.
 

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Discussion Starter · #5 ·
No, that's it. Do you have a flash hider you can try in place of the adapter? It does sound like either the barrel or adapter may be out of spec.
I'm afraid I don't.

I spoke with a friend who has a CMMG barrel as well and he was kind enough to pull it from his gun to measure it, and it's exactly at 10 and 3/8" on a tape measure. I measured mine at exactly the same length. Hopefully that means this is more an OOS thread adapter than barrel, as this barrel was (A) expensive and (B) one of the CHF/CL versions.
 

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Discussion Starter · #9 ·
So barrel length being the same as my friends, that means either the FN receiver or the CMMG adapter is off somehow.

I'm hoping it's something as simple as the adapter being too deep, and can be fixed with either a shim or a new adapter.

Have receivers ever been reported as being off in such a way it would cause this? I'm assuming not but figured I'd cross it off the list.
 

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Never heard of a receiver being the issue. It is probably the adapter. That has been the culprit almost every time a similar issue has come up (that I've seen, at least).

Good luck getting it worked out. Post up what the issue was when you get it resolved.
 

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Discussion Starter · #11 ·
Never heard of a receiver being the issue. It is probably the adapter. That has been the culprit almost every time a similar issue has come up (that I've seen, at least).

Good luck getting it worked out. Post up what the issue was when you get it resolved.
Thanks buddy, I really hope so too. I will definitely post the results!
 

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If the barrel is REALLY 10 3/8" it's too short. The correct barrel length is 10.4" That said, you really can't measure that with a tape measure.
 

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Discussion Starter · #13 ·
Just updating: CMMG asked me for a picture, so I sent it to them and haven't gotten a response in about a week.

A local friend had a spare Hi-Desert Dog muzzle device he let me test and it stops threading exactly where it needs to.

At this point I think when it comes time to use the thread adapter I'm just going to put it on a lathe and take the shoulder back 1mm or so, assuming CMMG never responds. I guess the good news is at least it's not the barrel.
 

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If the barrel is REALLY 10 3/8" it's too short. The correct barrel length is 10.4" That said, you really can't measure that with a tape measure.
There's more than 0.025" of float in the factory configuration. He obviously doesn't have a micrometer, much less one that can measure something over 10" long. Forgive him if he can't discern twenty-five thousandths of an inch difference with his naked eyes.
 
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