Googled the heck out of it.  Answers are mixed, and most point to just using barrel vise blocks.  That's fine but I think I'll have to remove the gas tube.  The thing is, one gentleman noted that the barrel extension runs in the same direction as a muzzle device so that putting torque on the muzzle device is fine (won't rotate the barrel extension).  Is that accurate?

(Putting on a Silencerco muzzle brake).

Thanks!

BEV block is for barrle nut, use the vise block to hold the barrel when working on the muzzle.

A barrel can be loosened from the extension 

Channeled soft jaws for a barrel in a vice.  Got mine from Brownells here: http://www.avantlink.com/click.php?tt=cl&pw=55963&ctc=j1y70xdk5i00zk8a00y51&mi=10077&url=http%3A%2F%2Fwww.brownells.com%2Fgunsmith-tools-supplies%2Fgeneral-gunsmith-tools%2Fvises-accessories%2Fvise-jaws%2Fmagnetic-soft-jaws-prod22513.aspx

You should be able to put the barrel in the vice as close to the muzzle as possible without having to remove the gas tube, unless you've got a shorty.

Just get the magpul vice block. Zero movement.

Hi, To answer your Q, no it's not accurate. The reason The extension won't unscrew is because it's on the barrel at 150 ft lbs torque. (But it happens now and then) Using soft jaws, or barrel jaws on the vise is the right way to install a muzzle device. The muzzle device, barrel and extension are right hand threads. As you turn the muzzle device to the right it gets tighter. If you're holding the assembly (extension, barrel, and muzzle device) by the extension as you tighten it to the barrel the extension will try to tighten. If in the same scenario you were removing a muzzle device, as you turn it to remove it, the barrel extension will also attempt to unscrew. Two pieces of wood with a V notch cut in them placed in the vise works good too. -CB

For muzzle devices, I have an aluminum barrel vice block, but haven't used it yet (just received it). What I've done in the past is just wrap a thin leather belt around the barrel and vice the s*** out of it. It's always worked for me.
I'd NEVER trust an upper receiver block, Bev block, Reaction Rod, or any of that stuff.

Don't spend any money.  Just wrap a thin strip of leather around the barrel just behind the threads and grip it hard, really hard in a bench vice.  Grip where the work is to be done, never at the opposite end of the barrel.

And of course the excellent advice you've received also applies to Reaction Rods... Geissele and others.

+1^^^

Also a block of wood drilled with appropriate sized hole then sawed in half makes a perfect set of bbl blocks.
Clamp as close to the muzzle as possible.

Eta: just assembled a shorty yesterday, no room for blocks. Cut a strip off an old leather belt, worked like a charm.

Clamp 2 soft pine boards together and drill press a .65-75ish hole down the seam where both boards meet.

Congrats you made a barrel vice.

It's fine as long as your barrel wasn't made by Radical Firearms

I'm guilty of using my BEV block for muzzle devices, but I'm usually the one who builds them so I try not to put them on too tight anyway