need help with barrel threads not working

[wsr]

wut?
i are not machiney

Different % of thread engagement

[PhotoTom]

wut?
i are not machiney

Is this a tolerance stacking issue?

Yes…stacked tolerances. If both the suppressor AND the Walther barrel are slightly out of tolerance, yet not enough to have an interference fit with a different "opposite" component that is in-tolerance…you could very well be seeing this situation.

[RifleGuy]

Contact the folks at Class III Machining. They can fix it, and affordably.

http://class3machining.com/

https://www.facebook.com/barrelthreading/

[Moleman-]

If it were me, I'd verify the thread pitch and get a nice quality split die. Most of the 9mm AR barrels are 1/2"-36tpi but some are 1/2-28 or even 5/8-24. Open up the die so that it doesn't take off any material, then slowly unscrew the adjustment screw 1/8th-1/4'turn each pass until the muzzle attachment just fits. It's likely going to be a tiny bit of material the die removes. Recently had to do that with a 5/8-24 barrel and a Silencerco brake. Just took a little bit of fuzz out of the bottoms of the V's. Likely would pass measuring using the 3-wire method as it didn't remove the finish off of the rest of the threads. Brake threaded on fine after that and the can was centered on a range rod.