Like the title says I need to be schooled on something that I’ve even doing for years and apparently wrong. I have about 7-8 years building ars for myself and I just found out via a brownells YouTube vid just this morning that I have been installing flash hiders incorrectly , Iv been using a mag block with the full ar assembled then clocking on the flash hider on. That’s the way I was taught by a gunsmith back in the day. I do use a torque wrench ,shims and a magpul armors wrench, bev block when I do uppers. I did hear that a bunch of stuff can shear/break off when you use the method I was using. I kinda freaked out and took apart all my ars and lowers and inspected them all ,they all look to be ok. No cracked lower takedown holes ( upper or lowers ) , no sheared barrel index pins and no cracked uppers. Was the way I was doing it a old school way or was the gunsmith just jurry rigging it? I even went as far as pulling out of storage and checking the first ar I built ( Anderson upper/lower set , spikes lpk, dpms carbine h barrel ) and everything looks to be ok even under a magnifying glass and flashlight. Am I just stupid lucky that nothing broke ? Obviously I will now be using the magpul bev block for both barrel nut and flash hiders now. I would imagine that the torque that it takes to clock on a barrel nut far exceeds what it takes to that of a flash hider ? Sorry for the long post, Any and all info is very helpful.

You're going to get a lot of opinions. This is what I use:
Barrel nuts on the left (with a large shop vise)
Muzzle devices on the right

BEV Block or Reaction Rod would be better than a mag block for installation.  You wouldn't have to worry about bending or shearing your index pin.  
Best of all would be to clamp the barrel in a vise.  

For removal, clamp the barrel in a vise.  Even a BEV Block or Reaction Rod won't save you if your barrel extension is under-torqued and you spin it loose.  
And NO, according to the mil-spec that's not supposed to happen, yet it has happened.

I actually have the BEV block but I’ve only ever been using it to install barrel nuts

MD work = barrel blocks for me. Always.

To each their own and there is more than one way to skin a cat, as with all things.  


FWIW, the largest is a stuck or over torqued MD during removal.

You want to isolate the part being worked on right?  So that means barrel blocks, period.  But hey its '
Murica do as you please.

If you control torque on installation, typically 25-35 ft-lbs, odds of causing an issue with even suboptimal methods is low.  On removal breaking torque can be quite a bit higher. It’s here that barrel blocks are the safest method to isolate torque, followed by a reaction rod that is supported in the upper, followed by a Bev block.  Vise blocks for barrels can slip.  Good contact area and use of rosin can help.  So can prepping the removal with penetrating oil, heat, or hot water soak for Rocksett.  

I note on my builds torque value applied during muzzle device install and whether any thread locking compound was used.  Settling on simple, effective muzzle devices precludes the need to swap muzzle jewelry around.

I got one of these over 5 years ago, used it on many builds, rebuilds, barrels swaps, muzzle device swaps, etc & never had a problem.  



https://www.brownells.com/gunsmith-tools-supplies/rifle-tools/bench-vise-blocks/ar-15-m16-upper-receiver-action-block-prod22385.aspx

Absolutely the wrong fixture for muzzle device work, end of story.  Call yourself lucky so far, remembering that luck always runs out.

Attached File

True...  you can loosen or over tighten the barrel extension using a receiver block for muzzle device work.  Barrel blocks are the right fixture.

Always clamp as close as possible to what you are working on.