So I'm looking to install a new warcomp on my 17. Sooner or later my RC2 7.62 can will get out of jail so I want to make sure I install this correctly.

My Google searching has told me a few different things.

From what I gather the black crush washer is being installed first, with the beveled edge closest to the muzzle device. Do I still install the thicker spacer and shims after the crush washer? I've seen a few videos where they only installed the black crush washer and cranked till the ports were facing 12:00.

No crush washer!  Just follow the instructions with the Warcomp and use the included shims to time it with proper torque.

It says in the instructions manual for the Surefire muzzle device "With SCAR-H, use supplied spacer with chamfer facing away from the barrel."

I forgot the SCAR 17 uses a jam nut.  It is different than a crush washer in that it does not “crush” when torqued.  So use the jam nut and then the shims to time per instructions.

Yes the instructions say to use the spacer with chamfer or bevel facing muzzle device. Do they want the the thick silver spacer installed first, then the black crush washer on top of that? PMM sells the black crush washer specifically from surefire for the scar 17. It looks like PMMs video only shows the crush washer when they are installing a brake.

I've seen no mention of using the original jam nut.

I'm not sure if you're referring to the crushwasher from the factory, but you don't use any crushwasher for a suppressor mount or it will be misaligned -- always use shims. You just take off the crushwasher from the factory. Crushwashers are one-time use only, so you would use a new crushwasher even if this wasn't for a suppressor mount.

Maybe it's what they consider the spacer, but it looks like a normal ar15 crush washer. Maybe this is a different material. It's black with a bevel, chamfer, tapered side. Other side is flat.

So if that is considered the spacer, do I still use the thicker zinc looking spacer plus whatever shims are needed after it? As in barrel, black spacer, thick zinc spacer, shims, muzzle device.

The SCAR barrels are too thin to mount a silencer or QD device to naturally. For 5/8x24 tpi threads, you really need .750" at the shoulder with a .725" absolutely minimum. The SCAR is like .660".

To adjust for this there are manufacturers out there that sell custom precision washers. They look like crush washers because they're tapered, but really they're a precision "adaptor" that takes your .660" or whatever and turns it into .750" so you have the mounting surface for a can on a thin barrel.

So long as this is what's being talked about here, this is very important to be the first thing installed on the barrel.

You'll want to go barrel->Precision Washer/expander->peel washer/shims (for timing)->QD device.

An example of this is here: https://www.kbacustom.com/our-products/firearm-accessories/product/34-scar-17s-muzzle-shoulder-ring.html

It looks like a crush washer, but isn't. It's designed specifically to take your small shoulder and make it large enough to mount, along with the necessary parallelism/flatness to be safe for silencer use. My guess is that Surefire supplies one of these (or one like it) for SCAR use.

I've had to use this on a FAL and AK for this purpose, and it's worked wonders.

My 16 17 and 20's muzzle devices are installed as pictured, no aftermarket shoulder rings just the surefire supplied black beveled spacer + shims

Yeah that looks a lot like it expands the shoulder to an acceptable diameter. Good on them for including it - it's something most people don't know they need, but incredibly important to protect their investment.

on my ar the timing shims bunched up when installed facing the beveled side of the surefire spacer after being torqued to spec

I think I have it set up correctly now, just need to take it to my parents place so I can torque it down with my aac 3 prong tool.

Middle of top ports are sitting at 5:30 hand tight which looks like about where it should be on surefires diagram.

I have the black spacer with beveled end facing muzzle device, 2 no color shims, the large green shim, then warcomp. So as long as they expect to get half a turn when torque is applied I should be good. Easy enough when actually doing it.

Does the 5:30 thing include the use of a crush washer? For the silencer specific mounting hardware, nothing should crush/deform, so I would be very surprised (and worried) if I got a half turn after hand tight. It should be close to locked up already.

Maybe I'm missing something.

My advice to you is to contact Surefire directly. A gentleman named Paul Glass, their suppressor project manager, was able to provide shims that allow for the muzzle device to time against the muzzle, not the shoulder.

Back ground: I purchased my SCAR 17 in 2012, installed a Surefire FH using a reverse washer (that Surefire recommended before KBA had their shoulder ring)  in 2013 when I got my SOCOM 762 can. Over 2000 rounds, the shoulder became deformed and the muzzle device lost concentricity with the bore. I had Parker Mountain Machine look at it, and I’m uncertain as to what they actually did other than use a KBA shoulder ring. Regardless, 500 rounds later it lost concentricity. Surefire was able to square up my muzzle and install a new 5/8-24 SOCOM 3 prong flash hider using muzzle shims. It is all good now, but Surefire does not sell the muzzle shims to the public.

Your other option (and most logical) would be to buy a Dead Air Keymo SCAR 17 flash hider with a Sandman. Their FH times against the muzzle, not the shoulder of the barrel.

Don’t repeat the same mistake I suffered if you intend on shooting suppressed mostly as I do. I recommend sending to Surefire if you intend on using a SOCOM can. If not, use Dead Air with a muzzle device that times against the muzzle, not the crap shoulder that FN gives us.

Does surefire include the spacer on all of their 7.62 variety socom muzzle kits?

Unless something has changed in the past few months, yes.

Thanks, Ive ran mine unsuppressed since i’ve got it but this new B&T rbs can looks pretty appealing

Figured I should come back and update this lol. I installed it super easy. With the green shim starting at 5:30ish was way off. I removed the green and did 2 no colors I believe. Which I could get hand tight around 10 o'clock. At 30lbs I was just ever so slightly short of 12 o'clock and my ocd wouldn't allow that so I ended up with a torque of 35lbs to hit 12 o'clock. Still no suppressor yet, so I can't be positive but with my geissele suppressor alignment rod it looks dead center in the muzzle device.

Thank you for this this post. I took a closer look at mine because of it.

Looks like I was headed for the same issue. Mine probably only has 250 rounds through it if I had to guess. Less than 500 for sure. So I don't think any damage was done. (Yeah I know I need to shoot it way more). I will check it with my surefire bore alingment rod after I'm able to torque the flash hider down. I just broke my dad's $50, 30+ year old bench vice before I was able to do that haha got the money's worth out of that one for sure.

With wrong spacer backwards (done by Gun Gallery Jax around 2013. Not very tight or any rocksett either..)


With the proper spacer in the correct orientation. Flat part towards the barrel chamber. Bevel towards the muzzle device.


As said above my post, these black spacers come with all the 762 socom muzzle device adapters now. I used one of these black spacers on a 16in sig 300blk barrel too. The sig barrel has a weird taper so the spacer goes with the bevel toward the barrel chamber instead of toward the muzzle device like on the scar17. I've never needed this spacer on anything else.

Surefire really needs to do what Dead Air did: make flash hiders and muzzle brakes that also time to the muzzle and not the shoulder of the barrel. KeyMo is the way to go on pencil barrels as I painfully found out. In my defense, KeyMo was not available in 2012-13 when I purchased my SCAR 17 and Surefire SOCOM 762. I don't understand the logic given the popularity of the platform and of Surefire suppressors.

Again, I would call Surefire and send them your barrel to have them do it. Paul Glass is the man.

I emailed surefire this morning expressing my concerns with a link to this thread.

Thanks again Mao

Good day, i know this is stupid question but I can't find any information on a web..

Why use anything when you a "jam nut" on Scar 17?

I'm planning to install dead Air "muzzle brake" and was hoping to only use the original "jam nut" similar to how the original Muzzle brake was secure.

i never took it out so there is something I'm missing i will assume as you all using SCAR FLASH HIDER  or shoulder ring sets...

Please educate me

The jam nut may not be exactly “square” to the face of a flash hider or muzzle brake that indexes to the shoulder of a barrel. The FN jam nut may be ok to use a PWS muzzle brake, but not good enough for a suppressor adapter. Likewise, unless torqued appropriately to the muzzle device, it can become loose with time.

Now having said, the muzzle nut on my Galil ACE is beefy, and I was able to have a gunsmith (with the correct vise and tools), time a Surefire flash hider to the IWI factory muzzle nut, as IWI instructed me to do. IWI meant their muzzle nut to time muzzle devices apparently. Way back when in 2013, Surefire told me it was a no go with the Scar’s muzzle nut and to use their washer reversed (this was before the KBA shoulder ring). FN of course simply told me to screw myself and that I would automatically void my warranty either way.

If you are planning on using a Dead Air, they make SCAR 17 specific flash hiders (and scar 16) that index to the muzzle and not the shoulder. It will cost you more in the long run if you don’t do it that way (as I found out the hard way).

Thank you for your response, I guys i don't have an option but to get the " SCAR 17 specific flash hiders" that dusk lol as i really like the muzzle brake for recoil reduction etc!!!

Ask Dead Air:

https://deadairsilencers.com/product/keymount-muzzle-brake/

I would also ask JMAcs

https://www.jmac-customs.com/shop-by-product-type/muzzle-devices/

OSS makes muzzle brakes that index to the muzzle and not the shoulder as well

Thank you !!!

Wanted to bump this thread rather than create a new one.

I recently purchased a NRCH scar 17 and bought a dead air scar flash hider. I read either here or on the FN forums that some of the NRCH muzzle threads were being reported shorted than normal, resulting in muzzle devices that index off the muzzle making contact with the shoulder.

So my question is, is there a way to confirm that the dead air device is in fact indexing off the muzzle and not the shoulder? I am able to screw the device down until no threads are visible and then apply torque, just would like to be sure.

Measure the threads on the inside of the flash hider and on the outside of the barrel to compare. Also, are you using the Dead Air SCAR 17 specific flash hider on your SCAR? Todd MaGee posted about this somewhere a month or so ago. Call Dead Air for help.

It is the Scar 17 specific flash hider. What’s the best way to measure the threads inside the flash hider? Figure calipers for the muzzle.

I will shoot Dead Air an email as well.

Well that is a good question. If you have a similarly threaded barrel with long threads, you could mark off how far the flash hider screws onto the barrel until it reaches the end point. You could also estimate it by using a small ruler inside the flash hider’s threads and eye ball it. I’m sure someone on here has a link to a special tool to measure thread depth.