Installation and removal of the barrel nut is the highest torque operation on an AR-15/M16 M4, AR-10, 308 AR type rifle. For this to be successfully accomplished, the upper receiver needs to be properly secured.
While upper receiver blocks for the AR-15/M16 M4 series of rifles are shop staples, many shops may not have access to upper receiver blocks for an AR-10/308 AR. Even if they do, with the wide range of upper receiver designs, using the wrong set of blocks can possibly damage the finish. If you don’t have the right blocks, don’t worry, you can always remove a barrel nut with a barrel vise.
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Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.
Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.
We recently had a Cerakoted upper come through the shop and we didn’t want to mark it up. Rather than risk damaging the finish, we decided to grab the upper by the barrel (below).
I used our Farrell Barrel vise in the shop press to grab the barrel. This allowed easy removal of the barrel nut for a repair (the rifle was manufactured without a ejection port cover in place, installation required removal of the barrel). Note, I used some white paper as a shim between the barrel and aluminum to prevent marring the surface. I also needed to invert the top jaw of the vise so it would be small enough to grab the AR-10 barrel.
You can purchase the Farrell Barrel Vise from Brownells.