I built a couple AR-s today but I have one question about whether I did the flash hider correctly.  When I finger tightened it, the solid portion was on the bottom so I knew I had to go beyond that.  Midway's video says to tighten it until "Center cut is straight up".  What's the center cut?  In their video the wrench flats are approximately vertical but not actually; he has the solid portion slightly to the side of centered on the bottom.

My first AR I built, years ago, I aligned that solid part on the bottom, openings on the top.  This time, though, I aligned the solid part on the top, openings on the bottom - it seems that having the flash blocked on top might be the right choice but it sure wouldn't match the pictures.  To get it where it is now, I had to tighten in the vise just over 90 degrees.  To get the solid portion on the bottom, would require another 180 degrees of tightening.  I'm not sure I could get it to go that far without damaging the barrel alignment pin in the barrel extension.

One more question.  I have read often about the trouble people have getting flash hiders off so, on only one of the two, I put anti-seize compound on the barrel threads.  What are your thoughts on doing that?

A2 device is designed for solid part at the bottom, to prevent dust kickup while firing prone.

A modern crush washer allows near-constant torque after initial contact, to get things aligned correctly with proper torque. The old style peel washer needs to be modified by peeling layers, if necessary, to get the correct torque with the correct orientation.

I don't use anti-seize on barrel threads for flash suppressors, nor do I recommend, but I don't think it'll hurt anything, either.

first off you did use a crush washer right?

there should be five slits or cuts for the flash to escape through on that flash hider. the solid part goes on the bottom and center slit/cut goes at the top in line with the gas port/gas tube. if you used a crush washer you simply tighten it to where the center slit/cut lines up with the center top of the barrel after the flash hider makes contact with the crush washer.



this is what it looked like when it made contact with the crush washer I then tightened it till the center cut lined up with the gas tube. you can see the gas tube on the backside of the wrench in the picture. it was about 3/4 of a turn more to get it lined up after contact with crush washer. I do put a drop of rockset on the threads but a drop of locktite would also work but probably is not necessary.



ETA,  also you want to use barrel vise jaws to hold the barrel while tightening the flash hider, never use the barrel extension pin and upper to do this. you could rap a piece of thick leather around the barrel to protect it and clamp it in the vice just be careful not to mar the barrel up. my barrel clamp is made of aluminum so it's softer than the barrel and does not mar the finish.

Attached File

The "wrong" way to do it but I'm lazy and don't have neat things like a work bench and vise and such....

But I use a split washer and just do it by hand, no tools, etc.  Check alignment every few hundred rounds while cleaning, have never seen one change position.  Granted, just shooting 556 and 9mm (perhaps 308 recoil can do something different?) but it works for me.

Thanks for the great replies and pictures.

I've ordered a Wheeler barrel clamp for my vise.  It should be in in a couple days.  I'm going to the range in the next day or two, weather permitting, so I'll probably shoot first with the flash hider upside down.

I am sure I used crush washers; I have both peel washers and crush washers on hand but I used the crush washers.  It's good to know it doesn't require additional torque to complete the job.  I'll do that when the clamp comes in.

I ordered a pack of 20 additional crush washers just to keep on hand in case I have to start over.

I wondered about the anti-seize.  That's why I did it on one and not both; just to see what happens.

Hopefully I can post some pictures and follow-up by this weekend.

Following this thread, I'm installing an A2 flashhider on a 308 AR and the FH is at 1:00 when finger tight. I guess I can do a near full revolution on the crush washer to get it at 12:00?

Correct. Crush washer is meant for up to 450 degrees of rotation (all the way around plus 90 degrees).

3 posts up from yours. ^^^

Straight from the TM. No "guess".

OK, yeah, now that I'm on the laptop I can read the "450 degrees" in the image. GTG

You can make a barrel block out of couple of 2x4s, IMO the wood blocks wok better than some of the ones you can buy.

Hmmm, I hit 90 degrees of rotation and torque jumped up to 90 foot/pounds and higher so I quit. I added a second crush washer and got where it needed to be without excessive torque. Maybe the 308 AR crush washers aren't the same rotation values as the AR15.

Not all CWs are equal. Some are too stiff causing torque values to skyrocket or result in CWs cracking. Ebay is full of them.

I got both vise mounts - already had a couple of the upper blocks that wrap the upper but now I have the barrel vise block and the vise block that attaches to the upper like the lower.

The lower-style block wasn't helpful for this because it required turning against the alignment pin.  The barrel vise block is pretty bad for a pistol build.  The only place to attach the vise block is forward of the gas tube block except that the vise block is longer than the space available for my 11.5 inch barrels.  I had to remove the gas tube (good thing I found gas tube pins $6.00 a hundred at Grainger) and put the barrel vise block behind the gas block.

No matter how tight (I literally picked up myself on the vise handle) I tightened the vise, the barrel spun in the barrel clamp, damaging the finish on the cheap AR Stoner barrels.  Had it been my beautifully finished Rosco barrels I would have been pissed.

I was really blaming the clamp but then I pulled the flash hider and replaced the crush washer with another from a different supplier and then then was able to tighten the flash hiders to the proper alignment practically with ease.  Still, the risk of damaging a barrel is significant.  You won't know if it is gripping your barrel until it doesn't - and then it's too late.

In any case, the builds are complete and I shot them both at the range tonight.  I only had about an hour to set up, shoot, pack up, and get out, before they closed so I couldn't site them in or shoot as many rounds as I hoped but they both functioned beautifully.

Short bbls usually require handguard removal.

Rosin, a strip of leather/rubber aids in preventing bbl spin.

What block did you use?

And yeah,  all crush washers are not created equal.  Shims are my go to.

I've started using shims as well.

I used the Wheeler barrel vise block.

Call me lucky, or whatever, but I've never had a problem timing a MD with a crush washer.

when timing your flash hider/ brake simply loosen and retighten the flash hider a little at at a time as to avoid galling the barrel threads. Many folks want to keep torquing until the the brake is timed accordingly. As long as you have compression against the CW you are fine.

Crush washers are not designed to be tightened/loosened/tightened.

Shims > crush washers, IME.