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Posted: 3/24/2009 2:03:47 PM EDT
I have three new barrels (threaded 1/2 X 28) and three flash hiders - two vortex, one Noveske KX3. There is one combo, the exact one I need to work, where the KX3 will not screw onto a particular barrel without cross-threading. All other combos work with no hesitation, roughness or even a hint of cross-threading.

Does It seem like I need to re-tap the threads on the KX3?
Link Posted: 3/24/2009 2:17:56 PM EDT
Let me see if I understand you correctly.
You have 3 barrels. All 3 flash hiders work on 2 barrels.
On the third barrel the 2 vortex flash hiders work and the KX3 does not.
Sounds like bad threads on the barrel.
Link Posted: 3/24/2009 2:38:17 PM EDT
Originally Posted By SandHillsHillbilly:
Let me see if I understand you correctly.
You have 3 barrels. All 3 flash hiders work on 2 barrels.
On the third barrel the 2 vortex flash hiders work and the KX3 does not.
Sounds like bad threads on the barrel.


Yep, you got it. The challenge is to determine which threads are corrupt. The barrel threads look cleaner, so my guess is that the KX3 is the culprit. I ordered a tap/die set from Brownells - hopefully a little cleanup will solve it.
Link Posted: 3/24/2009 2:49:03 PM EDT

Originally Posted By bradharper:
Originally Posted By SandHillsHillbilly:
Let me see if I understand you correctly.
You have 3 barrels. All 3 flash hiders work on 2 barrels.
On the third barrel the 2 vortex flash hiders work and the KX3 does not.
Sounds like bad threads on the barrel.


Yep, you got it. The challenge is to determine which threads are corrupt. The barrel threads look cleaner, so my guess is that the KX3 is the culprit. I ordered a tap/die set from Brownells - hopefully a little cleanup will solve it.
Or the threads on the barel are slightly undersized.

Link Posted: 3/24/2009 5:06:03 PM EDT
What's the serial # on your KX3?

It seems that I'm having issues with mine, #06266, threading on my Noveske barrel.
Link Posted: 3/24/2009 5:23:40 PM EDT
Originally Posted By unclemoak:
What's the serial # on your KX3?

It seems that I'm having issues with mine, #06266, threading on my Noveske barrel.


Mine is #05846 (~ one month old). I wrote and heard back from Noveske today, and they implied that some barrel threads tend to be over sized where as the KX3 is slightly undersized. I guess I just have a combo with an extreme mismatch. I hope the tap/die from Brownells will take care of the issue. I'll let you know how it works out.


Link Posted: 3/24/2009 8:27:14 PM EDT
Use ReconBob's trick for assembling barrels onto Thompson receivers - pick up some valve-seat grinding compound from the auto parts store and smear onto the threads of the barrel. Work the FH back and forth a few times. Get it started straight. Once it goes on to the end, clean up the threads real good. It will screw on easily.....You can make grinding paste from oil and some of the carborundum "dust" from under your grinder!
Link Posted: 3/27/2009 3:20:24 PM EDT
I got the Brownells tap today and re-cut the threads on the KX3. There was definitely a difference according to the tap - enough that the barrel would only go in up to the point where I'd tapped. After a full pass all is well.
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