Try pushing the pin straight back, towards the rear of of the rifle.

The threads should be 14x1mm LH.

If your pin doesn't push in, take some pics so we can see what we're dealing with here. BSW

It would be helpful to see exactly what yours looks like to know what is going on.

If your detent pin is protruding a bit from the FSB like in the picture you posted the link to then it is engaging a detent milled into the muzzle device to keep it from turning. The pin is spring loaded and will push back into the FSB like shown in my picture below. If your is protruding and stuck you might want to try a little penetrating oil and some light taps to free it up. Once you get it pushed in the muzzle device will be free to turn. Remember that the threads are left hand so it will unscrew clockwise.

I know it is a different rifle but my NHM-90 muzzle originally looked like this:



The detent pin was in the FSB but it was pushed all the way back by the "thread protector". The thread protector was then tack welded to the FSB to keep it in place since threaded muzzles were prohibited by import restrictions.



A few minutes with a dremel cut-off wheel took care of mine.

Your pin may have been modified to lock the thread protector on in order to do away with the threads for import purposes. Never heard of that before but it's possible I suppose. The pins will come out left to right. might try a little penetrating oil and let soak over night. Even with the pins out the FSB sometimes still must be pressed off. You can use a gear puller with a brass fitting to protect the muzzle. To install a new detent pin you will have to remove one of the pins but not the entire FSB.

I have a feeling this is the answer. I'll try and pound that pin out in the next few days

well i got the punch pin and tried to pound the pins out (left to right) and they wouldn't budge so what is the deal?

You might try to get the pins out by going right to left as our NHM 91 was like that.Mad Max son of Madtechcool

I got a tapco brake to replace the muzzle nut and the stupid thing wont fit! It screws on but after about three turns it gets very tight. I checked the threads and they don't have any burrs on them is it possible that my NHM-91's threads are off? or has anybody heard of tapco screwing up threads before?

I have bought a few muzzle nuts and slant breaks from a few sources that were threaded improperly (or were not the pitch i ordered). It is not uncommon. Try again with another and remember LH.

Did the muzzle nut screw on okay for a few turns and then lock up? If so, try another one. I have had to force some before at about 1/2, but be careful. Better to try another nut or break than to damage the barrel threads. The threads could have been turned down and then rethreaded 1/2 x 28 RH (same as ARs). Look at the muzzle nut thread pitch and the barrel and see if they line up or not. If 1/2 x 28 RH, try cncwarrior. They are great to deal with and have what you need.

Close up pictures of the barrel threads will help us tell what you have. What is the exact outer diameter of the barrel at the treads? Is it at or less than 0.5"?

Just curious as I have an NHM-91 with the same solid pin setup, wouldn't removing it make it non-compliant with 922 unless you swapped out the rest of the needed parts with US made stuff?

went with US made stock, grip, hand guard, muzzle device, and 3 fire control parts - overkill!