problem install yhm hand guard

[tdaughg]

im trying to install a rifle length yhm hand guard on a bohica upper and the jam nut doesn't want to thread all the way down. the factory barrel nut on the bohica is a yhm nut so i know that part is right. the hand guard seems to thread down just fine. i can get the jam nut past the first portion of the threads on the barrel nut most of the way by hand and then i have to use the forearm wrench to get it that last little bit. when i try to thread it onto the second set of threads (closest to the chamber) it will only go on 2-3 threads and then it locks up. i cant even get it to go with the wrench.

im wondering if anyone else has encountered this and if so how they fixed it? on the other hand can i leave the jam nut off and just thread the hand guard down and use a drop of loc-tite on it?

[CRTguns]

make sure the handguard is on the right end (both are threaded inside).

The nuts can get bent up sometiomes by over-zealous barrel-tightening.

[ar15barrels]

The most common cause I see of damagd YHM barrel nuts is using a two prong barrel nut wrench with very short pins.
The proper YHM barrel nut wrench has 3 pins and they are longer so they spread the load through the nut.
The shorter pins distort the nut right at the end where the lock ring goes.
The result is described in the original post above.

The solution is to replace the barrel nut, or lap the locking ring to the damaged barrel nut to try to correct the existing part.

[tdaughg]

got the hand guard on the right way and it threads on just fine. the jam nut is whats being a pain.

ar15barrels: could i just leave the jam nut off and loc-tite the hand guard?

[joelogic]

Trust me you dont want to loc-tite the hand guard. I see a snapped gas tube in your future. I would know, I snapped one.

[tdaughg]

Trust me you dont want to loc-tite the hand guard. I see a snapped gas tube in your future. I would know, I snapped one.

no gas tube. bohica .50 dtc bolt action upper

[ar15barrels]

ar15barrels: could i just leave the jam nut off and loc-tite the hand guard?

I suppose you could, but the handguard is probably not going to cover the whole barrel nut without the lock ring.

[adamsreeftank]

Did you cross-thread the lock nut. Maybe if you remove the barrel nut and screw the lock nut on from the back before you tighten the barrel nut it would work better.

[BSlacker]

On YHM barrel nuts with two separate threaded areas the jam nut threads on the barrel nut from the end closest to the upper. Get it 1 or 2 threads away from the upper to start then install the forearm in your desired position and tighten jam nut.
The YHM barrel nut separate threads are not timed to thread the jam nut on from the front end.
Do not use locktite. Once heated a few times it won't hold just when you need it.

[tdaughg]

...The YHM barrel nut separate threads are not timed to thread the jam nut on from the front end...

i was thinking the same thing. heres the problem with that though. i have 2 barrel nuts. one that came with the hand guard kit and the one that is factory installed on my upper. the factory one is whats causing problems. the one that came in the kit seems to be just fine. the jam nut threads across both sets of threads just fine.

ive got an email in to bohica to see what they have to say about it. thanks for the info everyone.