I recently bought A2 handguards from H&R and when I tried installing them on my Armalite AR10, they don't seem to want to close all the way. They are fine in the front though.
What should I do to get them to fit? Wanted to get a diagnosis/solution for this before I start dremeling anything.

AR-15/M-16 handguards?  On an AR-10?  Is that dimension the same, even tho the nut is larger?  I don't have a large frame.

I don't know about the A2 round hand guards, but with the A1 Triangular hand guards, you need the early originals off the A1 M16's.  The heat shields are tapered and get large enough at the back to clear the Armalite AR-10 barrel.
The later ones (or maybe they are reproductions) have heat shields that have parallel sides all the way to the back and won't clear the Armalite AR-10 barrel diameter (at the base).

Tony

Update, even removing the heat shields did not resolve the issue. Maybe the channel in which the handguards slip over the teeth of the barrel nut is too shallow? I bought a set of OEM Armalite handguards from EveryGunPart to see if the factory handguards have the same problem.

A little dremel work and they fit now!