Flash hider will not thread in all the way?

[glen]

I have an AR barrel I installed a flash hider on. Threaded on fine but after a few turns it got much harder to twist. The hider was still quite a way from the crush washer at this point.

I put a flat washer before the crush washer and timed the flash hider. Properly timed, the flash hider ended up about 0.185" from the barrel thread shoulder. Crush washer did not "crush" and was more to cover the exposed thread. I was twisting pretty hard at this point to get it to time.

What are possible causes for this sudden tightening after a few turns? Could I have damaged anything?

[Iraqgunz]

You need to lock the upper down into a vise and properly install it. You do not need anything other than a crush washer unless you are putting something special on.

You need to get an armorer wrench and some anti-seize. Apply anti-seize and then then put the FH on. Use the wrench and tighten it down.


I have an AR barrel I installed a flash hider on. Threaded on fine but after a few turns it got much harder to twist. The hider was still quite a way from the crush washer at this point.

I put a flat washer before the crush washer and timed the flash hider. Properly timed, the flash hider ended up about 0.185" from the barrel thread shoulder. Crush washer did not "crush" and was more to cover the exposed thread. I was twisting pretty hard at this point to get it to time.

What are possible causes for this sudden tightening after a few turns? Could I have damaged anything?

[glen]

You need to lock the upper down into a vise and properly install it. You do not need anything other than a crush washer unless you are putting something special on.

You need to get an armorer wrench and some anti-seize. Apply anti-seize and then then put the FH on. Use the wrench and tighten it down.

Forgot to mention that the upper was in a receiver block at the time. I understand that it should have been in a barrel vise though. Tightening was done via armorer's wrench.

IG, as I understand I should install upper in barrel vise, remove flash hider, apply anti seize on barrel thread, put on crush washer, thread on the flash hider till it contacts crush washer, then twist to time?

What I had done was I had the upper on a receiver block, then hand tightened the FH. It hand tightened fine for about two turns, after which it required an armorer's wrench and lots of effort to twist on further.

Appreciate the info on the proper install, I'd also like your insight on the possible causes of the sudden tightening. By twisting on at that point could I have damaged anything? Anything out of the ordinary or does it occur time to time given enough barrels and muzzle devices?

[Col_Crocs]

Id take it off to inspect both the barrel and FH threads to check for any pre-installation damage. That may be your cause. I think it would have to be pretty severe to cause such tightness though.
From how you describe it also sounds like one of the parts has the wrong thread pitch.
If you no way of measuring either thread pitch, you could try another FH or comp just to see how it goes onto your barrel and your FH on another barrel.
As for possible damage during installation, Your FH will most probably have taken most of it.

[Iraqgunz]

It happens sometimes. You should be able to see if it is cross threading or if there is some damage to the threads.

I have put flash hiders on before and though there was no way in hell and once I put the wrench on and started turning then it started moving.


Forgot to mention that the upper was in a receiver block at the time. I understand that it should have been in a barrel vise though. Tightening was done via armorer's wrench.

IG, as I understand I should install upper in barrel vise, remove flash hider, apply anti seize on barrel thread, put on crush washer, thread on the flash hider till it contacts crush washer, then twist to time?

What I had done was I had the upper on a receiver block, then hand tightened the FH. It hand tightened fine for about two turns, after which it required an armorer's wrench and lots of effort to twist on further.

Appreciate the info on the proper install, I'd also like your insight on the possible causes of the sudden tightening. By twisting on at that point could I have damaged anything? Anything out of the ordinary or does it occur time to time given enough barrels and muzzle devices?

[glen]

Col, I did a cursory inspection on both muzzle and flash hider prior to install, no damage apparent at the time.

Pretty sure it's not cross threaded, I believe there would be a cant if it were and the flash hider looks to be straight on the barrel.

Doing some research, I believe the possible causes are gunk/excess finish on the flash hider threads or the flash hider was threaded with a tapered or plug tap instead of a bottoming tap which would cause shallow threads towards the bottom of the hole and give symptoms that I experienced. Hoping people with experience on threading/tapping can chime in on this.

When I have time I will also be removing the flash hider from the barrel to see if any of the above possible causes was it.

[Belmont31R]

I would get something to measure your parts with. Stick something inside the flash hider to the "shelf", and mark it. Then stick that against the threads where the "shelf" on the barrel is. Usually with no shims or washers most 5.56 devices (1/2x28) will thread all the way again the barrel shelf/shoulder or about 1/16" within the shoulder/shelf.



If the threads are clean I would just get a new muzzle device. Its easier to replace that than the barrel. If its just an A2 you can get them from many sources. I recommend BCM A2's and crush washers.



If something is not right with the muzzle device with the threading, and you attempt to push past the blockage you could destroy the threading on the barrel. Id clean both thoroughly with solvent, thread is on dry, and see if things don't improve. Sometimes Ive installed devices where there was some residual rocksett or whatever and it was a bit harder to turn. Once you do the final install with something like an A2 you want a anti-seize grease on the threads.

[M90A1]

I ran into this problem once with a BC 1.0. Any other FH would thread right onto the barrel, but the BC would only go a short way before getting horribly tight. I ordered myself a 1/2-28 tap and die from Ebay, ran the tap into the BC, and that was the end of the problem. Everything fit fine and continues to run perfectly many hundreds of rounds later.

[Clint]

Sounds like something slightly out of tolerance.

Many things can affect this, including finish build up, machining errors, thread contamination and heat treat warpage.

Either:
the barrel's major dia or thread pith is too big or thread is too short/ incomplete.

Or
the flash hider's minor dia or thread pitch is too small or thread is too Shallow/incomplete.

Try to check each option.

If you have another flash hider, try that.

You can run a tap into the FH to clean it up.

You can mic the bbl threads.

You can hit the bbl threads with a scotch brite wheel to clean those up.

Good luck.

[Evil Bert]

What kind of FH? Who is the Manufacturer? Why don't you just call them up and explain. If they are a decent company, they will send you a new one, etc.

[glen]

Thanks for all the suggestions guys, problem has been solved.

I removed the flash hider, and the threads were fine. Flash hider thread was tapped all the way to the inner shoulder.

Wiped muzzle and flash hider threads clean, then tried screwing it on and this time it turned freely till its old final position and got unusually tight again.

No access at the time to a 1/2-28 tap so I got a paper clip and used the end to chase the threads of the flash hider. There was a fair amount of gunk that was freed up.

Test fitted and the flash hider now threaded easily by hand to the end.

Put some anti-seize and the crush washer and the flash hider spun easily to the crush washer. 1/4 turn to index and done.

Glad the problem was just gunk and not any tolerance or specification differences.

Oh, and the flash hider was a Troy Medieval I got a good deal on. I was more interested in finding the technical reasons and effect of this than to complain, and for the record I did email Troy and Bob got back to me promptly and offered to replace it if the problem was with the flash hider. Im sure they would come through if needed as they always have in the times I've contacted them.

[Clint]

Glad you got it worked out.

Thanks for posting back.