BOSS theory indicates that moving the BOSS device along the barrel changes the vibration frequency. The "Sweet Spot" is when the bullet exits the barrel at the top or bottom of the vibration wave, which is the time that the barrel experiences the least motion. (Sweet Spots vary with bullet weight, powder loading, caliber, manufacturing lot and other ammunition variations.)

Precision accuracy from the BOSS system is achieved by calibrating your rifle caliber and ammo with a "sweet spot" setting. The "sweet spot" settings in your BOSS owners manual were determined through extensive testing by the Browning Research and Development staff. "Sweet spots" may vary between rifles of identical specifications with a given ammunition. Even one quarter of a turn away from the "sweet spot" can cause a group to spread as much as one inch or more. We suggest you use our listed "sweet spot" setting as a starting point in determining the exact "sweet spot" setting for your particular rifle and make adjustments accordingly.

Note: any change in BOSS setting may slightly alter your rifle's point of impact. It's recommended you set the BOSS "sweet spot" setting before sighting in your rifle for windage and elevation. The BOSS was tested in full turn, 1/2 and 1/4 turn increments. Tighter groups may be achieved with the BOSS tested in other positions.

Preliminary Adjustments
Before setting your "sweet spot," it is important that your BOSS is calibrated with the barrel. This will ensure that your rifle is consistent with those tested by Browning Research and Development when BOSS "sweet spots" were determined.

To find out if your BOSS needs to be calibrated, loosen the micro-adjustable locknut and turn it until it bottoms out on the threads of the BOSS -- or will not loosen any further.

If your BOSS is calibrated, the "0" on the micrometer adjustment ring will line up with the longitudinal hatch mark on the barrel .

If the "0" isn't aligned with the longitudinal hatch mark, you will need to calibrate your BOSS. Move the micrometer adjustment ring on the bottom of the micro-adjustable locknut so that the "0" is aligned with the longitudinal hatch mark. To adjust the micrometer adjustment ring, insert your finger nail or a small pointed object in the split of the ring and rotate the ring.

Setting your Rifle to the "Sweet Spot"

Full turn "sweet spot" settings or graduations are numbered 1-10 and inscribed on the barrel of your rifle.

Smaller, 1/10 turn increments are inscribed on the micrometer adjustment ring.

To set the "sweet spot," the micro-adjustable locknut is turned either clockwise or counterclockwise until it is aligned with the desired "sweet spot" number inscribed on your rifle's barrel. One full revolution of the micro-adjustable locknut indicates one full change in setting or one index mark on the barrel. 1/10 turn increments are set by rotating the micro-adjustable locknut until the desired setting lines up with the hatch mark on the barrel.

IMPORTANT: When adjusting the "sweet spot" make sure you grip the knurled surface of the locknut. The knurled portion of the micro-adjustable locknut and micrometer adjustment ring must rotate together to ensure a precise "sweet spot" setting and retainment of proper calibration.

Caution: When setting the "Sweet spot" on your rifle make certain your rifle is fully unloaded and that the rifle's safety is in the "on safe" position and your rifle is pointed in a safe direction.

EXAMPLE 1 --

1. Suppose you have a 270 caliber A-Bolt II rifle and are sighting in with 150 gr. cartridges. After zeroing out the BOSS as explained previously, refer to the "sweet spot" chart where you will find the average "sweet spot" is 6.0 for a 270 A-Bolt II with 150 gr. ammo.
2. After having made sure your BOSS is calibrated properly on the barrel, rotate the micro-adjustable locknut counterclockwise six full revolutions. The edge of the micrometer adjustment ring should line up or rest on the marking for 6 on the barrel of the rifle.
   NOTE: It is not necessary to calibrate your BOSS on the barrel with each change in "sweet spot" setting. However, you should check the BOSS periodically to assure proper alignment.
3. Since the "sweet spot" is listed at 6.0, the 0 inscribed on the micrometer adjustment ring should line up with the hatch mark or longitudinal line on the barrel.
4. Tighten the body of the BOSS so it is secure against the micro-adjustable locknut. Use the special wrench supplied with your rifle. Insert the wrench through one end of an exhaust hole and out through another. It is recommended to insert the wrench through the smallest set of holes possible. Turn clockwise until the body and micro-adjustable locknut are tight .

Caution: Remove the wrench from the BOSS exhaust holes before firing your rifle. Failure to do so can cause injury to yourself or others.

EXAMPLE 2 --

1. Suppose you have a 300 Win. Mag. BAR Mark II rifle with Federal 180 gr. cartridges. After zeroing out the BOSS as explained previously, refer to the "sweet spot" chart where you will find the average "sweet spot" is 2.5. 
2. Calibrate your BOSS and rotate the micro-adjustable locknut counterclockwise until the edge of the micrometer adjustment ring lines up or rests on the marking for 2 on the barrel.
3. Since the "sweet spot" is listed as 2.5, the 5 inscribed on the micrometer adjustment ring should line up with the hatch mark or vertical line on the barrel.

Using the special wrench, tighten the body of the BOSS so it is secure against the locknut. Your BOSS system is now calibrated for Federal 180 gr. ammo using a 300 Win. Mag. BAR Mark II.