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Discussion Starter #1
With previous SCARs and the thin profile of the barrels it has been required to use a shoulder ring to get suppressor mounts to go on the barrel. Just received my latest greatest generation Scar 20 308 with the newer barrel profile (1-10 308 twist, not stepped ) and I don't believe a should ring will be required. Has anyone had any experience with this setup and mounting a suppressor break?

My barrel diameter on the new SCAR 20 at the muzzle before the threads is 21.3mm vs my old SCAR 17 of 16.9mm.

2 other notes as I've seen it asked...
1. the new muzzle break was easy to remove with zero heat or water and hardly any force.
2. the gas block as shipped appears to be a 1.5


Thanks,
Chris
 

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The shoulder ring was necessary due to the very short barrel shoulder on the 17S barrel, needed more for a suppressor brake/flash hider to seat against properly for alignment. Since your new barrel has roughly .2" of shoulder you'll be totally fine seating any kind of suppressor muzzle device. Since I use TBAC suppressors I know their spec. and they just want .125" shoulder.
 

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My new SCAR 20S in 6.5 Creedmoor came with a Surefire Procomp muzzle brake AND a shoulder ring the same diameter of the barrel at the muzzle. The muzzle brake EASILY broke free after applying a little Aerokroil to it but the shoulder ring itself was not loose and it seems to be permanently affixed to the barrel, so I left it on and after applying a little anti-seize to the muzzle threads, screwed the YHM 2130-24 QD 5/8"-24 flash hider down and torqued it to 30 ft./lbs. DO NOT apply any type of Loctite or Rockset to the muzzle threads prior to screwing on the muzzle device. You WILL come to regret that decision. Just check the tightness/torque of the muzzle device prior to and during shooting the firearm. You WILL be wanting to remove the muzzle device more times than you imagine and if you've used Locktite or Rockset you WILL end up hating yourself more than your ex does...
 

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Huh, I always add red loctite to all my suppressor brakes/flash hiders. Don't want them accidentally coming off with my suppressor. Maybe it's just the type of suppressors I using vs ones that have some sort of ratcheting locking ring on them. I mostly use Thunderbeast Ultra's on my rifles.
 

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Huh, I always add red loctite to all my suppressor brakes/flash hiders. Don't want them accidentally coming off with my suppressor. Maybe it's just the type of suppressors I using vs ones that have some sort of ratcheting locking ring on them. I mostly use Thunderbeast Ultra's on my rifles.
When properly torqued, the muzzle device will not come off and as a good rule of thumb you should ALWAYS check the tightness of the muzzle device prior to and during shooting, whether or not Locktite/Rockset is used. They aren't lock and forget...
 

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Discussion Starter #6
Archmark
My new SCAR 20S in 6.5 Creedmoor came with a Surefire Procomp muzzle brake AND a shoulder ring the same diameter of the barrel at the muzzle. The muzzle brake EASILY broke free after applying a little Aerokroil to it but the shoulder ring itself was not loose and it seems to be permanently affixed to the barrel, so I left it on and after applying a little anti-seize to the muzzle threads, screwed the YHM 2130-24 QD 5/8"-24 flash hider down and torqued it to 30 ft./lbs. DO NOT apply any type of Loctite or Rockset to the muzzle threads prior to screwing on the muzzle device. You WILL come to regret that decision. Just check the tightness/torque of the muzzle device prior to and during shooting the firearm. You WILL be wanting to remove the muzzle device more times than you imagine and if you've used Locktite or Rockset you WILL end up hating yourself more than your ex does...
@ Archmark, That shoulder ring you said would not come off was a crush washer. That was the most difficult part to remove on my rifle. If you google crush washer removal you will find plenty of suggestions to remove. I simply put some oil on the threads and grabbed the crush washer with a set of vice grips and unscrewed from the barrel while the barrel was in a vice while pulling quite hard.

Conventional wisdom advises against using a crush washer with a suppressor. Your results may be fine.

Regarding locktite, I usually use red when adding a muzzle device and never have an issue when time to remove after applying a little heat.

Thanks for all the suggestions. Good info from everyone.
Chris
 

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Archmark


@ Archmark, That shoulder ring you said would not come off was a crush washer. That was the most difficult part to remove on my rifle. If you google crush washer removal you will find plenty of suggestions to remove. I simply put some oil on the threads and grabbed the crush washer with a set of vice grips and unscrewed from the barrel while the barrel was in a vice while pulling quite hard.

Conventional wisdom advises against using a crush washer with a suppressor. Your results may be fine.

Regarding locktite, I usually use red when adding a muzzle device and never have an issue when time to remove after applying a little heat.

Thanks for all the suggestions. Good info from everyone.
Chris
My alignment rods from McMaster-Carr should arrive today so i'll be checking the alignment. If in fact it is a crush washer, then what is the difference between it and the "shoulder ring" sold by Parker Mountain Machine and Surefire and included with their Warcomp flash hiders for installation on SCARs? They look identical. With 20-30 ft/lbs. torque, I woud doubt that there is much "crush" in the ring. I'll find out for sure once I check the alignment...
 

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You obviously know what a crush washer is. The PMM ring for SCARs is a solid steel ring, NOT designed to crush or deform, that provides a larger surface shoulder for a suppressor muzzle device to shoulder against. It's a precision machined part that provides the perfect flat face for alignment of the muzzle device.
 

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You obviously know what a crush washer is. The PMM ring for SCARs is a solid steel ring, NOT designed to crush or deform, that provides a larger surface shoulder for a suppressor muzzle device to shoulder against. It's a precision machined part that provides the perfect flat face for alignment of the muzzle device.
Well, the "ring" that came on my SCAR 20S 6.5 Creedmoor seems more like a "shoulder ring" than a crush washer to me. It appears to have all the attributes if what PMM & Surefire offer, not like the "crush washers" offered by Sig to "time" their muzzle devices for their SRD556 QD line of suppressors. Mine's not thin or flexible, it's a rather substantial manufactured piece of metal. I guess it could be a crush washer as the 6.5 Creedmore comes with a Surefire Procomp muzzle brake, not a flash hider, and could be used to time the MB. With the thicker profile heavy barrel of the SCAR 20S 6.5 Creedmore barrel, I'm now wondering if a shoulder ring would even be necessary for SCAR 20S?
 

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The only reason "we" added rings to 17S barrels was due to the lack of needed shoulder to seat a muzzle device against. Again I'll use the TBAC suppressor spec as an example, they want .750 diameter for their muzzle devices to get the flat support needed to ensure solid alignment and obviously the 17S barrels aren't remotely close to that. Your 20S barrels sound great and I see no reason to put the ring on them from your description.
 

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PMM's shoulder ring is the best...its a surefire...

Rocksett is just fine...if you ever need to remove it...all you have to do is set it in boiling water for 15-20 minutes...easy...comes off with little to no trouble...

However the new barrel profiles do not need a shoulder ring...you will be fine without one.
 

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PMM's shoulder ring is the best...its a surefire...

Rocksett is just fine...if you ever need to remove it...all you have to do is set it in boiling water for 15-20 minutes...easy...comes off with little to no trouble...

However the new barrel profiles do not need a shoulder ring...you will be fine without one.
Thanks, that's what I thought. Now if I can just get the shoulder ring/crush washer off without ****ing up the muzzle threads & barrel. It didn't want to budge when I tried to remove it by hand. Tomorrow I'll try sliding a real thin flat blade screwdriver under it and "walk" it off.

I did receive some toys for it my SCAR 20S 6.5C today: an Atlas bipod & monopod, an A.R.M.S. #19 picatinny QD rail to mount my Leupold Mark 4 ER/T 6.5-20x50mm M5-A with the 34mm tube & American Rifle Company M10 low scope rings and 6.5C & .556 tool steel rods from McMaster-Carr for checking the alignment of the bore to the YHM R2 suppressor. The scope's 50mm objective was just a tad to large to clear the SCAR's rail, so I had to get the A.R.M.S. #19 to raise the scope up enough to clear. Now there's all of an 1/8" clearance between the rail and the front flip cap. Tomorrow the Pelican Storm iM3200 case and a couple of 20 rd. mags are due to arrive and that will finish things off for me, except for an aftermarket lower receiver if I can find one. I've got literally hundreds of SR25/M110 20 rd. mags and I don't want to really invest in many of those crappy, overpriced FN proprietary mags. STUPID idea on FN's part!!! I'm betting there are mag supply issues over in the sandbox that us Joe 6-Pack civilians are never gonna hear about. I know the last thing I ever thought about was retrieving expended M14 mags because I could always get all I wanted from the Supply Sergeant, so FN really screwed the pooch with their mags.

With the one box of 6.5C ammo that I could find, I might just make it to the range on Saturday and bust her cherry. Might as well take the Garand too because 20 rounds of 6.5C will last all of 20 minutes at the most.

Thanks again for the info...
 

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Discussion Starter #13
@jaflowers - You mentioned using a Thunderbeast can. I will be using an Ultra 5 on my 308 scar and curious what gas jet you found to work for your can with the SCAR 20?

@archmark To remove my crush washer I put some oil on the threads, barrel in a vice then used a large set of vice grips to grab the crush washer from the muzzle side of the barrel and while pulling unscrewed the crush washer. It took a bit to bite but did work. The screwdriver idea I tried and it was useless.
 

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Can you share the part numbers?
6.5 Creedmoor - 8893K202 Tight-Tolerance Multipurpose Oil-Hardening O1 Tool Steel Rod, 0.2460" Diameter, 3 Feet Long
5.56 - 8893K191 Tight-Tolerance Multipurpose Oil-Hardening O1 Tool Steel Rod, 0.2120" Diameter, 3 Feet Long

Prices sure beat the hell out of buying one from Geissele...

138328
 

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Thanks, that's what I thought. Now if I can just get the shoulder ring/crush washer off without ****ing up the muzzle threads & barrel. It didn't want to budge when I tried to remove it by hand. Tomorrow I'll try sliding a real thin flat blade screwdriver under it and "walk" it off.

I did receive some toys for it my SCAR 20S 6.5C today: an Atlas bipod & monopod, an A.R.M.S. #19 picatinny QD rail to mount my Leupold Mark 4 ER/T 6.5-20x50mm M5-A with the 34mm tube & American Rifle Company M10 low scope rings and 6.5C & .556 tool steel rods from McMaster-Carr for checking the alignment of the bore to the YHM R2 suppressor. The scope's 50mm objective was just a tad to large to clear the SCAR's rail, so I had to get the A.R.M.S. #19 to raise the scope up enough to clear. Now there's all of an 1/8" clearance between the rail and the front flip cap. Tomorrow the Pelican Storm iM3200 case and a couple of 20 rd. mags are due to arrive and that will finish things off for me, except for an aftermarket lower receiver if I can find one. I've got literally hundreds of SR25/M110 20 rd. mags and I don't want to really invest in many of those crappy, overpriced FN proprietary mags. STUPID idea on FN's part!!! I'm betting there are mag supply issues over in the sandbox that us Joe 6-Pack civilians are never gonna hear about. I know the last thing I ever thought about was retrieving expended M14 mags because I could always get all I wanted from the Supply Sergeant, so FN really screwed the pooch with their mags.

With the one box of 6.5C ammo that I could find, I might just make it to the range on Saturday and bust her cherry. Might as well take the Garand too because 20 rounds of 6.5C will last all of 20 minutes at the most.

Thanks again for the info...
That sounds awesome, Mate... Please post pics when you have it all together... Cheers
 

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Thanks, that's what I thought. Now if I can just get the shoulder ring/crush washer off without ****ing up the muzzle threads & barrel. It didn't want to budge when I tried to remove it by hand. Tomorrow I'll try sliding a real thin flat blade screwdriver under it and "walk" it off.

I did receive some toys for it my SCAR 20S 6.5C today: an Atlas bipod & monopod, an A.R.M.S. #19 picatinny QD rail to mount my Leupold Mark 4 ER/T 6.5-20x50mm M5-A with the 34mm tube & American Rifle Company M10 low scope rings and 6.5C & .556 tool steel rods from McMaster-Carr for checking the alignment of the bore to the YHM R2 suppressor. The scope's 50mm objective was just a tad to large to clear the SCAR's rail, so I had to get the A.R.M.S. #19 to raise the scope up enough to clear. Now there's all of an 1/8" clearance between the rail and the front flip cap. Tomorrow the Pelican Storm iM3200 case and a couple of 20 rd. mags are due to arrive and that will finish things off for me, except for an aftermarket lower receiver if I can find one. I've got literally hundreds of SR25/M110 20 rd. mags and I don't want to really invest in many of those crappy, overpriced FN proprietary mags. STUPID idea on FN's part!!! I'm betting there are mag supply issues over in the sandbox that us Joe 6-Pack civilians are never gonna hear about. I know the last thing I ever thought about was retrieving expended M14 mags because I could always get all I wanted from the Supply Sergeant, so FN really screwed the pooch with their mags.

With the one box of 6.5C ammo that I could find, I might just make it to the range on Saturday and bust her cherry. Might as well take the Garand too because 20 rounds of 6.5C will last all of 20 minutes at the most.

Thanks again for the info...
Use a torch. Heat up the flash hider...comes off easy. FN doesn’t use rocksett to my knowledge...but high heat removes gas jets and flash hiders.

I had a crush washer issue on a POF once...monkeyed on...I just went back and worth until it came off.
 
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