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Posted: 9/7/2010 6:22:38 PM EDT
I had my PS90 barrel cut down by TROS and they threaded the barrel end as M12x1 Lefthanded. They included the adapter for 1/2-28 but I wanted the P90 look so I ordered the one from CMMG (it's also supposed to be M12x1 Left)

Just tried putting the CMMG on tonight and it does not fit. It barely starts threading and then just stops. The TROS one can be finger tightened all the way down.

I got out the metric thread-pitch gage and both of them are the correct 1mm pitch, both are left handed threads. I don't have any calipers but they both visually take the pitch gage to the same depth.

The ONLY thing I can see is that the TROS parts have more of a triangular threadform and the CMMG part is more trapezoidal. On the CMMG piece the crests of the threads have a visible flat.

Has anyone else had this problem?



Link Posted: 9/8/2010 4:15:17 AM EDT
[Last Edit: 9/8/2010 4:16:55 AM EDT by ezielinski]
I had my barrel cut back by TROS, and had no problem screwing on the CMMG P90 flash hider (except I forgot that it was LH...)

Link Posted: 9/10/2010 6:24:10 AM EDT
Buddy of mine cut down my factory barrel. I ordered a CMMG 1/2x28R thread adapter. Fits fine. But CMMG isn't exactly known for good barrels.
Link Posted: 9/10/2010 10:15:32 AM EDT
Sounds like their threading tool had a broken tip and you have shallow threads.
Send it back and have them chase the threads or get a replacement.
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