I had a zero shift on my Fulton M14, after I got home I noticed there was a bit of play in the flash hider assembly and castle nut. is there a good way to tighten it without the proper tool that Fulton sells?

Thanks in advance.

Brownells sells the tool for $17.00 and that is worth it's price for getting the job done RIGHT.

Now, you CAN tighten it without the correct tool if that's what you choose (not my choice tho).  


Secure the barrel in a strong padded vice and apply Kroil, etc. just to loosen things up. Next, loosen

the locking screw that secures the castle nut so it allows the nut to turn. Take a brass punch and place

the tip at an angle on one of the cut-outs where the correct tool would be inserted. Tap with a hammer

to turn the castle nut one way or another. Personally, I would remove everything, clean and inspect,

then re-install. Next, reinstall the flash hider and screw the castle nut as tight as possible with fingers occasionally

tapping it rearward with a block of wood, etc. to seat it. Now you can use the brass punch again to tighten

the nut until sufficiently tight....you'll have to be the judge of that. The castle nut will need to be timed so

the lock nut will engage one of the cut-outs at the front of the castle nut. A little coat of grease on the barrel

splines is good as is BLUE Loctite on the locking screw....not the castle nut its self.

Most of the flashider pliers sold now are garbage made in  China.  Worth it to find USGI.  

Also, before tightening make sure to release the set screw.

Ya it bought this used and I can't understand why there is grease on the castle nut assembly. A coat of CLP is good but what looks like old lithium grease? Not suprised I have to do this.

The castle nut should only be hand tight without the aid of the “pliers”. The set screw holds it in place. The pliers should only be used to loosen.

Like SAN mentioned, a brass punch and a tack hammer will work fine. If I didn't get my pliers cheap, I wouldn't have bothered.

I would say no on the loctite.  It’s just too small, next time someone goes to,loosen it without knowing it needs to be heated up it will simply strip the allen socket.

Just my opinion on little screws.

I would definitely avoid loctite on the little set screw.

As stated, don't bother without the tool. There's no real reason for someone with an M14 or M1A not to have both the castle nut pliers and gas cylinder wrench. As stated above, take the flash hider assembly completely off. Do not forget to loosen that setscrew, it's easy to forget. Unthread the nut and pull the assembly off. Clean it and look for any damage. Then put it back together. I don't use grease. Put the assembly on and tighten the nut by hand. Once it feels snug, take a rubber mallet and tap the end to seat it fully on the barrel. Then tighten the castle nut with the pliers until snug, plus turn until the next notch on the nut lines up with the set screw. Put the set screw back in. There's no torque spec, it's turn until the next notch. It shouldn't be that hard to tighten.

I recommended BLUE Loctite for the specific reason heat is NOT required to remove a screw

or bolt that was treated with it. I have never had to use heat to remove a screw that

BLUE Loctite was applied.

And while it is not required on the set screw, I have shot enough rounds through M1a's

to have seen them back out.

The grease under the flash hider will prevent rust on it and the barrel should things get wet

and helps with removal should you want to do that. Yes, the parts are parked or blued but

I have seen the splines get down to bare metal upon installation.

OP, this is important.

Technically, the flash hider is held on by both its fit against the splines and the castle nut.  So you may want to peen the splines to tighten it up, then put the castle nut on.

So if I can't quite index the castle nut with the locking screw, what is the play? is it possible to shave off a hair of the castle nut so it can lock? It needs like 1mm more rotation to get the proper indexation in one of the slots, backing it off I lose all the tightness.

That would be one way to do it. Or get a few more castle nuts and see if one of them has better thread timing for your barrel/flash hider combination.

Are you sure your flash hider is all the way seated?

Ya, I tapped it with the mallet, torqued the shit out of the castle nut. It is just not quite there for the locking screw to index.

If you are in the Midland, MI area, come on by and use mine for free

Oh I got the right wrench now, thanks though. That isn't the issue.

I use purple locktite (222) on small screws I plan on having to possibly remove at some point as I’ve had allen screws, especially small ones, strip using blue.

I don't know a much, but this is not something I have experienced. There really shouldn't be that much force to get the nut from finger tight to the next notch. It's only 1/8 of a turn max, it really shouldn't take that much. If you really cant turn it that far I would have to think something is messed up either in the threads or the splines.