I recently took an AR upper to have a Surefire brake installed. I've always done this myself but this time my tools were indisposed and I was short on time. No worries, $30 at the local gun store for them to install it.

Anyway, when I picked it up they had placed the brake onto my barrel without a crush washer. I've always used a crush washer and always seen devices installed with a crush washer. But I'm not an expert, and they insisted it was good. It shoots fine and is timed correctly, so I ask the brain trust: have I always incorrectly assumed crush washers are required? Is there any issue relating to screwing a muzzle brake directly onto a barrel?

If it's timed correctly and has the proper torque, then no, there shouldn't be an issue.

Tony.

Surefire muzzle devices come with a shim kit you're supposed to use to time the brake correctly when installing. This includes one thicker chamfered shim that goes on first against the barrel's shoulder followed by however many thin shims it takes to time your MB.

I'm pretty sure the install instructions specifically state not to use a crush washer though I don't have them in front of me..

If they didn't use the shim kit I'd get my money back and take it to a competent gunsmith. Furthermore if they threw away your original packaging with the shim kit in it, I'd be doubly pi$$ed..

None of the Surefire muzzle devices use a crush washer set up like the traditional A2 flash hider. SF muzzle devices use a series of thin washers to establish the proper timing. The brake is then attached with the washers and loctite. This ensures that the device doesn’t move while attached/removing the suppressor.

The washers come me with the device and come in thicknesses that are almost tinfoil like to traditional washers.

Chances are it’s likely installed correctly.

I’ve actually messed around using the crush washer for a quick install to test a suppressor on guns before and it comes loose every time.

quote:

Originally posted by m499:
If they didn't use the shim kit I'd get my money back and take it to a competent gunsmith. Furthermore if they threw away your original packaging with the shim kit in it, I'd be doubly pi$$ed..

Shims are only there to correct for timing/torque errors. If you can get away with not using shims, that's always the best option. Shims are a separate part that's very thin. Shims can deform and become compressed. It's always best to torque directly to the barrel shoulder or the crown. It's rare that this happens, but always the most ideal situation.

There are shims that go on the shoulder and shims that go on the crown. If he can't see shims visibly, there's a good possibility that there are shims on the crown that will set the timing and torque.

Tony.

The shim kit includes a thicker "spacer" with a chamfered inner diameter that the manual says MUST be used on all SF mountings. It counter-acts the often rounded 90 degree transition between the threads and the barrel's shoulder giving the shims a perfectly flat surface to rest upon.

None of the 5.56mm SF muzzle devices are shimmed at the crown. I think there's only one 7.62mm version that is, but it's made specifically for the M240 MG.

If it’s a suppressor mount and you intend to mount a suppressor, you never want to use a crush washer.

Surefire non-suppressor muzzle devices do use a crush washer.

All the suppressor muzzle devices use the shim system as stated above. The thick shim is mandatory for barrels with a rounded transition to the threaded section.

BUT some new barrels have an undercut at the transition and technically do not need this washer.

Thank you for the replies. I should have clarified: I had the muzzle break on one rifle with shim and crush washer that I installed myself. I then took that upper to a gun store and had them remove it and place it on a different upper. When I received the second upper they had not used any shims (which I provided) or crush washer. I was just surprised is all, I've never seen a device directly onto a barrel without a crush washer. I'd thought a crush washer was required, but it seems I was mistaken. Also, the Surefire instructions didn't seem to indicate the shim was required but rather they were provided if needed for timing; it's been a while since I read them but that's how I understood it.

It's definitely tight and appears timed correctly. Perhaps 200 rounds through it's far with no issues. If an issue were to arise, what would it be? Just loosening of the device? Thanks

So did the brake initially come with a crush washer?

quote:

Originally posted by benny6:
So did the brake initially come with a crush washer?

You know, I don't recall nor do I recall what the instructions said about it. The rifle it was initially installed on I did place a crush washer there and shot probably 2000 rounds with no issues at all.

The crush washer is a way to avoid shimming to set the timing of the brake/compensator. Ideally the item should be torqued down to the shoulder. But to set an item, then remove it, figure the math to time the item properly, center it in a lathe and cut the shoulder back is time consuming. Hence the crush washer.

Maybe this has already been addressed and I just don’t follow, but when I got a TBAC suppressor the instructions were very clear that the muzzle device they offer to attach the suppressor to must be mounted on the barrel with peel washers, not a crush washer. I always assumed that was because a crush washer could result in a slight misalignment between the can and the bore, whereas the peel washers allow timing the muzzle device but also ensuring proper alignment.

Recognizing a peel washer, especially if it’s very thin might be difficult. In any event, I use peel washers with TBAC muzzle brakes that the suppressor screws to, and crush washers with the flash suppressors on the guns that I don’t use with the suppressor. Crush washers are less fiddly to deal with when timing a muzzle device, and any slight misalignment will not normally matter with something like a conventional brake or flash suppressor.

As a personal cautionary tale, the last time I mounted a TBAC brake on a new rifle that I intended to use with the suppressor, I reused an old peel washer. I assumed that even though the washer was a little beat up, tightening it in place would smooth out any defects. Wrong, and it took sending the muzzle device, can, and barreled rifle action back to Thunder Beast to get everything corrected.