The purpose of a RAS Muzzle Brake Tuning System is to reduce the felt recoil and improve the rifle's accuracy . The recoil reduction is built into the muzzle brake design. The improvement in accuracy is accomplished by turning the Tuning Ring as shown in figure 2. As the Tuning Ring is rotated the group size will change as shown in figure 1 below.
The following was shot in an AR15 with 16" barrel and 63 gr. Sierra SP bullets. With the flash suppressor the 2 shot groups averaged 0.96 inches. You can see the improvement with the RAS AR15 Mk III Tuner System.
An Index label has been provided with the RAS system to aid in this process (shown in figure 3). The Index label has marks 0.050 inch apart. It has been assumed that your rifle has either a 1/2-28 or 5/8-24 threaded tenon on the end of the barrel for a Flash Suppressor. If not a tenon will need to be added before a RAS system can be installed. For the larger barrels and larger RAS systems a 3/4-32 or 7/8-32 tenon will be required.