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 NHM-91 Muzzle nut removal?
DNS  [Member]
11/25/2006 10:26:29 AM
I have a NHM-91 that I would like to install a muzzle brake on. It has a muzzle nut on it without a functioning detent pin. It is not welded any where around it. The pin does not depress. The nut does not seem to move at all, no slop, or side play like one with a functioning detent. If I remove the sight pin will I be able to remove the pin? Also would the nut have something like locktite on it? Thank You
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JA545  [Member]
11/27/2006 9:03:24 AM
There is no Loc-tite on the muzzle brake threads.



In the above sketch the mbr pin has a notch in it to clear the front pin that holds the front sight base on the barrel. The notch allows it is slide in and
out of the front sight base. It has a spring so that the pin will come
out and engauge the notch in the muzzle brale to keep the muzzle brake
from unscrewing from the vibrations incurred when firing the rifle. To
remove or intall a muzzle brake you have to push the mbr pin into the
front sight base to clear the notch in the muzzle brake and hold it
while screwing/unscrewing the muzzle brake. Other wise it will catch the
notch in the muzzle brake and lock it in place.
But....... On most NHM-91 rifles instead of a pin with a slot in it to
allow the pin to clear the front sight base retaining pin so it could
slide in and out a solid pin was pressed in the front sight base. Also the spring for the mbr pin was not installed either.
Once you have the spot welds cut through you will have to remove the mbr
pin before you can get the muzzle nut off.
The easiest way to do this is to knock the front front sight base
retaining pin out. On both NHM-91 rifles I have done when the solid mbr
pin was installed it bent the front sight base retaining pin so bad that
I couldn't knock it out but had to drill it out. Center punch the pin
and use a 3/32" dril bit to drill 3/4 the lenth of the pin. Then use a
1/16" punch to knock the pin out. Then insert a screwdriver blade
between the muzzle nut and mbr pin and bend the pin up. Pull on it with
pliers till it stops and use the screwdriver to bend the pin up some
more. Repeat this several more times till you pull the mbr pin all the
way out then use vice grips,channel lock,or a pipe wrench to unscrew the
muzzle nut. Remember the threads are 14x1mmLH and the LH stands for left
hand. So you have to turn the muzzle nut clockwise to unscrew it.
The mbr pin and fsb pin are both 3mm in diameter so you can either buy
new ones or make them yourself from a common 8d size nail. Which is easy to do by cutting the head off the nail and chucking it up in a drill. Then while it spins hold a file to it till you get it down to the correct diameter. Don't get to excited on filing down the nail as it is only 3.25mm so it won't take much turning to get it down to 3mm. The size of the notch in the mbr pin is not really critical as long as it will move freely when you push it in flush with the front sight base and come out enough to fill the notch in the muzzle brake. The spring from a Bic Click ink pen is the prefect fit for the mbr pin spring.
You can use a file to remove what is left of the spot welds on the front
sight base then use some cold blue to cover the filing marks up. Also
use the cold blue on the mbr pin and front sight base pin to make them
look like factory pins.
roc762  [Member]
11/28/2006 2:21:22 AM
What he said.

Mine had the correct slotted detent pin, only inserted backwards so that it would not depress.
ttman  [Member]
12/3/2006 8:24:00 PM
interesting.. did it have the spring as well?

Originally Posted By roc762:
Mine had the correct slotted detent pin, only inserted backwards so that it would not depress.
DNS  [Member]
12/4/2006 7:52:19 AM
I ordered a spring and detent, also the front sight pin in case I need them. I didn't want to to remove the nut until I have them in hand. Should come this week. I did notice that there are no spot welds on the nut at all, at least that I can see. I hope it will come right off, and this doesn't mean there are no threads.
ttman  [Member]
12/4/2006 9:32:55 AM
hey take some pics of the process & post here. how much were the parts?
tk421  [Member]
12/24/2006 11:44:51 PM
What's the thread pitch on these? I'm going to take the nut off mine too, and replace it with a flash suppressor, but I want to actually have all the parts in hand before starting (got too many other things disassembled right now, don't need to add to it). And I need to know which one to buy.

Thanks.

Thanks. I was looking for a FS and found two or three different types of threads. Wanted to make sure before I bought one.

JA545  [Member]
12/25/2006 8:44:30 PM
All AK-47,AKM,and RPK rifles have the barrels threaded 14x1mmLH.
Metric thread sizes are expressed as the diameter in milimeters seperated by a (x) from the thread pitch which is the distance between any two corisponding points on one thread to the next thread in milimeters.
When the thread size if followed by a (LH) it denotes that the threads turn to the left instead of the standard which is to turn to the right.
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