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1/2 Inch Shim Kit for FOSSA-556 Flash Hiders

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Essential Kit for Properly Timing Suppressor-Ready Flash Hider

White Sound Defense’s shim kit provides an easy solution to the proper orientation (timing) of muzzle devices. Each shim adjusts the orientation of the muzzle device just over 1/8th of a turn, making it easy to select the number of shims needed. There is no need to mix and match various thicknesses to get the right adjustment.

The shims feature a slight cone shape, so they naturally align to give a finished look. The shims are made from high quality hardened stainless steel and are suitable for suppressor mounts. Because the shims are all the same thickness, you can combine spare shims from various kits to make use of extras.


Ensure the firearm is unloaded. Place the firearm in a fixture suitable for barrel work, such as a vice block. Install the muzzle device on the barrel without any shims or washers using only hand tightening. Estimate of how far the muzzle device needs to be rotated counter clockwise, to be in the proper place.

Each shim will rotate the muzzle device (counter clockwise) just over 1/8th of a turn. For example, if the muzzle device is a half of a turn past where it should be then, try 4 shims to back it up a bit over half of a turn. The number of shims may vary slightly depending on your barrel and exactly where it aligns. Once the device is shimmed within 1/8th of turn of center, apply any thread locker desired, and tighten into position.

1/8th of a turn past hand tight should be within torque specs for muzzle device installation. If you have difficulty bringing the device into position, try loosening and retightening the device a couple of times and this may make fitment easier.


  • Simple To Use
  • Hardened High-Temp Stainless Steel
  • Designed So Spares Can Be Combined


Q: Are shims better than crush washers?

A: Sometimes. Shims are a more stable way to install a muzzle device than crush washers. However, crush washers do fine in most instances. If you are mounting a sound suppressor using a muzzle device, White Sound Defense recommends the use of shims as they are more temperature stable and less likely to work loose causing a baffle strike.

Q: Does it matter which way the curve of the shim is oriented?

A: It is not critical, but it is preferred that the concave (bowl shaped) side is touching the shoulder of the barrel and the convex (domed) side is touching the muzzle device.

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