I haven’t received the handguards yet so not sure if the instructions will say…
I have to remove the FSB to install this handguard, this means removing the flash hider. Is replacing the crush washer neccessary? Is loc-tite adviseable on the flash hider if I don’t replace the washer?
Do I leave the handguard cap off (Round type) or reinstall ?
Leave the original handguard cap off.
I don’t think loc tite is adviseable, the heat generated during firing will negate the adhesive and you’ll have a loose flash hider.
I believe someone told me that crush washers are one shot affairs. It’s cheap and doesn’t cost much to replace.
Go to this link: http://www.ar15.com/forums/topic.html?b=3&f=4&t=226782
Scroll toward the bottom of the link for YHM installation demonstration.
Thanks for the link!
I think I should change the crush washer then.
Appreciate the reply
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What model is it? I have the Diamon specter and their standard carbine length free float. If you have the one piece unit, you will also need to remove the delta ring and barrel nut. You’ll install the YHM barrel nut/free float nut, put the locking ring on, then thread the free float on, screw it down with the retaining screws, then put your FSB on then your muzzle device. You will need a new crush washer or your muzzel device will not line up correctly.
I got the YHM-9479 regular Carbine length. I have the barrel stripped right now and just need to take it back to work with me to reinstall / torque everything down. I threaded everything down to see how it fits and I’m happy, just want to clean everything up before I reinstall. Will have it together by the weekend and I’ll post pics 
The crush washer is a problem… I can’t find one anywhere and will have to put it back as best as possible till I can get a new washer, or buy a new muzzle device 
If you have a flat bastard file you can remove some metal from the front and back of the crush washer. This may help getting the FH lined up.
You have fun with that mine was a pain. I had to take my AR to a local shop to get them to brake the tourqe on the original barrel nut and have them tighten down the new nut.
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I destroyed the barrel nut on mine trying to get it off. The teeth were just sheering off. Ended up getting 2.5 foot cheater bar extension.
I really like the YHM stuff.
So much so, that I’m building a rifle now with a YHM lower and upper. IF I can actually find a YHM barrel I’ll be all set as I’m going to reuse my YHM carbine length free float quad rail set up I took off the other gun to put the diamond specter on.
Got it all installed, all in all I like it. I put both lights on just for trial…
looks good