This precision shoulder Ring solves all of the issues with fitting muzzle devices and suppressors to the FN SCAR 17S rifle. Due to the small shoulder available on the SCAR 17S barrel from the factory, there are a very limited number of muzzle devices and mounts that will work properly. This ring increases the size of the shoulder by precisely bearing against the small factory shoulder. It also reduces the length of the muzzle threads to 0.60”, allowing any device or suppressor to be properly mounted. Shim kits and 5/8” peel washers can also be used to properly index muzzle brakes.

This Ring can also be used on other rifles with lightweight barrel profiles, very small shoulders, and standard 5/8” muzzle thread profiles. For reference, the OD of the SCAR 17S barrel at its shoulder is approximately 0.664”, and the thickness of this Ring is 0.112”.

Made of heat treated 17-4PH stainless steel and precision machined and finished to within 0.0005”, it provides a full size mounting face (OD = 0.750”) for your muzzle device/adapter/mount. It is Melonite coated in black.

Made in the USA.

Technical Notes:

• Do not exceed 25 ft-lbs of torque when using Rocksett or Loctite thread locking compound, due to the small bearing area between the Ring and the barrel.
• Before installation of this ring, ensure that the threads and the existing factory shoulder on the barrel are thoroughly cleaned of any debris. Besides being good practice, buildup such as old cured thread locking compound could possibly affect the alignment of the Ring’s face with the bore.
• After installing the Ring, or anything else over the muzzle, always check for proper alignment using a correctly sized bore alignment rod before firing. This will prevent any baffle or aperture strikes.

Instructions:

1. Verify that the SCAR is unloaded and made safe
2. Thoroughly clean the entire muzzle thread profile of any debris, such as dried thread locker
3. Slip the Ring over the muzzle with the OD chamfer facing away from the muzzle
4. If installing a brake, space out and add peel washers or shims as needed to index properly
5. Clean, degrease, and dry the threads on the muzzle, and in the muzzle device
6. Add a few drops of thread locker to the muzzle threads
7. Thread muzzle device onto the muzzle and snug ensuring the Ring is seated correctly
8. Torque the muzzle device, but do not exceed 25 ft-lbs
9. Before firing, always verify proper bore alignment of any muzzle device and/or suppressor!