For years, connoisseurs of Automat Kalashnikov (AK) pattern firearms have been unable to attach suppressors in a way that would allow them to align concentrically with their bore. The reason is due to the design of the AK and the way in which the factory muzzle device was designed to attach.
The AK uses a spring-loaded detent pin which protrudes from the front of the front sight post or gas block. This detent pin indexes into a notch, machined into the AK’s muzzle device and allows it to lock into place. It is completely normal for a small gap to remain between the surfaces of the muzzle device and front sight post, this is typical in most cases. This gap will cause a slight amount of movement or wiggle and is completely normal. In contrast, the muzzle device on an AR-15 pattern firearm is threaded on and torqued into place against a shouldered barrel. This shouldered barrel allows the AR-15 muzzle device to align concentrically with the bore, allowing a projectile to travel safely and unobstructed through a suppressor once attached.
Unlike the shoulder on an AR-15 barrel, the front sight post or gas block on an AK does not offer a concentric surface for a muzzle device to be torqued against. In order to achieve the same concentricity found on an AR-15 barrel, facemount devices were introduced.
Facemount devices achieve concentricity by indexing against the face of the muzzle. Assuming the face of the muzzle is cut square at a 90 degree angle, and the bore of the barrel was machined properly, a facemount device will allow a suppressor to be safely attached to your AK.
Some muzzle devices require to be installed in a specific orientation in order to vent gasses in the proper direction and function correctly, this is known as timing. Timing a muzzle device is an important step in the installation of most muzzle devices that utilize directional ports to mitigate recoil and should be conducted by a certified professional. The muzzle device on an AR-15 is timed using a shim set. A shim set is a series of circular steel shims that match the outside diameter of the barrel’s threads. Each shim set includes several circular shims in varying thickness which are designed to be stacked between the barrel’s shoulder and the muzzle device so that your device will align properly once the proper amount of torque is applied. Due to the nature of facemout devices, and the way in which they index against the muzzle face, standard AR-15 shims will not be compatible. In order to properly time a facemount device, a special facemount shim set will need to be used. A facemount shim set works similarly to a standard AR-15 shim set except that they’re placed between the muzzle’s face and the muzzle device, instead of the barrel’s shoulder and muzzle device, When installing a facemount device with a facemount shim set, an alignment rod is inserted into the bore to ensure the shim set maintains alignment as the devices is properly torqued into place. Unlike a typical AK muzzle device, a facemount device does not index against the detent pin, nor should it be touching the front sight post or gas block. A gap and visible threads between the device and front sight post is normal. If these surfaces were to touch, it would cause the device to become misaligned. Some facemount devices, such as the 360 and GFH, do not require timing or a facemount shim set, unless specific alignment is required for aesthetic purposes.
Facemount devices can be found in several different configurations to include GFH, GFHC, 360, 2C and 4C. Facemount devices are available in both KeyMount and X-Series configuration. Our X-Series devices allow the installation of suppressors directly to the muzzle devices with the use of external threads. Facemount devices can be identified by an “F” suffix after the thread pitch identifier of a device’s SKU (e.g. RRD-2C-14F-KM).
To learn more about facemount devices and how they work, take a look at the video below.
We recommend that our muzzle devices be installed by a certified professional to ensure proper installation and/or concentricity with your suppressor. Improper use of shims can cause misalignment. JMAC Customs highly recommend CW Gunwerks for the installation of our products.
Installation specs can be found on the compatibility charts listed below.