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Discussion Starter · #1 ·
I've been trying to research on methods to obtain a proper barrel shoulder for the Scar 17, but unable to find much information on what my options are to get a proper shoulder.

I am planning to run an OSS 7.62 can on my Scar 17. The OSS can that I have is the standard model, not tuned for the scar (Inside diameter of OSS Flash Hider is standard .308 size, not Scar 17 size).

I was told that I may get big POI shift if I did not have a proper shoulder. OSS said that I can send the can to them to get it tuned for the scar, but if I did so, I could not use the can on any other platforms besides the scar, as the internal diameter will be too small to fit other .308 rifles.

OSS said my other option is to turn down the Scar's PWS muzzle break's locking nut to .75 Outside Diameter to get a proper shoulder.

Does anyone know if there are any other options? Doing this will render the locking nut too thin to machine any flat surfaces on the nut, for any wrench to remove the locking nut later.

I'm all ears as to what you guys are doing for a proper shoulder.

Thanks!
 

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People are not doing much about not having a shoulder other than just running devices that index of muzzle. You cannot really run a Brake since there is no shoulder. You should not use the lock nut for suppressor use at all. Can you just take the lock nut off then thread on the OSS mounting device?
 

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I am planning to run an OSS 7.62 can on my Scar 17. The OSS can that I have is the standard model, not tuned for the scar (Inside diameter of OSS Flash Hider is standard .308 size, not Scar 17 size).

I was told that I may get big POI shift if I did not have a proper shoulder. OSS said that I can send the can to them to get it tuned for the scar, but if I did so, I could not use the can on any other platforms besides the scar, as the internal diameter will be too small to fit other .308 rifles.
The SCAR17 is a .308 rifle. How exactly are they going to tune a .308 silencer to not work on other .308 rifles by tuning the inside diameter? The inside diameter of what?
 

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Discussion Starter · #6 · (Edited)
must have something to do with the part of the oss can that goes back over the barrel?
Big Vick, yes you're right.

HK, what I mean is that the OSS can sits about 4.5 inches over the barrel. Inside the OSS can there's a mounted flash hider that also runs the length of the barrel. The standard OSS can that I have has an inside diameter that was made for a standard .308 barrel, not a scar barrel.


Here's a pic of the OSS flash hider muzzle break that goes inside the can. It's pretty much the guts of the OSS.


It's currently mounted without any locking nuts, just straight on. It seems solid, but I've haven't shot it yet as I wanted to make sure I was setting it up correctly.


 

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713, you don't want to use the jam nut for a stop point, their is no guarantee that the nut face is square to the bore. With it on the way you have it on now without the jam nut are you bottoming out on the muzzle crown (end of barrel) if so IMO that will be your best bet on alignment. I'm not familiar with that design, but with other flash hiders your GTG if your muzzle devise bottoms out like that, so if yours has a positive stop or shoulder in there and it's hitting the end of the barrel, I'm thinking that's your best route, if your not sure use some machine bluing on the end of the barrel and crank it on there, remove it and look inside your muzzle devise and confirm were the bluing has transferred, if it's on a shoulder in there that should be your best alignment. I would also recommend checking it with a bore alignment rod tool.
 

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Discussion Starter · #9 ·
Boom, thank you for this info, very much appreciated. I did not know that machine bluing exist. I will ask my friend who is a machinist if he has any machining bluing. Unfortunately, there is no contact on the muzzle face of my barrel to the muzzle device, but there is a distinct shoulder in the muzzle device. I've attached a pic to show the barrel muzzle threaded inside the muzzle device, and how it does not make contact on the muzzle end.



I've tried to use my calipers to measure the muzzle device's thread depth from shoulder to the end of the threads and it measured roughly 16.69mm. On the rifle's barrel muzzle, measuring from shoulder to muzzle face, I got roughly 16.2-16.4 mm.

I will need to use that bluing material to confirm the shoulder contact.
 

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Well since your not making contact on the muzzle obviously your bottoming out on the barrel threads. I don't know what that can is suppose to index off of, if it is in fact the barrel shoulder then Surefire makes a shim pack and included in it is a heavy spacer shim that they recommend for the SCAR 17 for use with the SOCOM, it's not real thick so you don't immediately notice it, but it will be the thickest one in there and it has a chamfer on the inside. This may be your fix, on the SCAR you actually install it backwards, chamfer toward the muzzle and you could use the shims to time your devise if required. You can buy this shim pack @ Silencer Shop. Good luck and be sure to check your alignment.
 

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Discussion Starter · #12 ·
Well since your not making contact on the muzzle obviously your bottoming out on the barrel threads. I don't know what that can is suppose to index off of, if it is in fact the barrel shoulder then Surefire makes a shim pack and included in it is a heavy spacer shim that they recommend for the SCAR 17 for use with the SOCOM, it's not real thick so you don't immediately notice it, but it will be the thickest one in there and it has a chamfer on the inside. This may be your fix, on the SCAR you actually install it backwards, chamfer toward the muzzle and you could use the shims to time your devise if required. You can buy this shim pack @ Silencer Shop. Good luck and be sure to check your alignment.

Boom, I see Silencershop has an AAC shim kit. Is this what you're mentioning?


AAC Shim Kits - Rifle Silencer Accessories - Accessories
 

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Hey no worries we just don't sell the SilencerCo shim kit separate. I took care of him though. Anyway you would think all shims are the same and come from the same place but there are at least 3 different ones that I know of.
 
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