I have an older AR10, with the round green carbon fiber float tube and 2-3/8" diameter black ribbed handguard nut.
The nut will not budge with every non-destructive method I've tried.
The nut looks identical in the photos of their current models using ventilated/rail type handguards, but they don't show the early smooth tube model anymore.  
Does someone make a wrench cut for this nut?

Has anyone worked with these?    Thanks.

EDIT:  PROBLEM SOLVED   The outer forend nut is captive on the barrel nut, just like a delta ring.  
The handguard tube itself is threaded.  
Turning the forend nut left or right (right hand thread) pushes or pulls the handguard tube on it's threads, with the handguard guide pin (in the bottom most hole in the barrel nut) keeping the handguard from rotating.   Severely simple once it's understood.


Thanks to the responding poster for sharing his experience, where it seems like the entire handguard and barrel nut was removed as an assembly.

I had the same forend on mine, careful application of heat to the nut (dont want to roast the fiber tube) and a large strap wrench on the nut. Use an upper vise block to hold the upper as it will take some torque to get it loose.

Armalite uses red thread lock on the barrel nuts and forends. You have to heat it up to get it to liquify. It just takes heat, and a good amount of it otherwise it wont budge. A small focused butane hobby torch works best and keep it moveing all around the nut. You want to heat it evenly.

Its a royal pain in the a$$ to get it loose, but take you time and everything comes off like it should and is completely reuseable.

I swapped mine for a DD lite rail...