THE BEST THERE ISTM BOSS OWNER'S ® MANUAL SWEET SPOT CHARTS FOR YOUR BOSS -EQUIPPED RIFLE ARE AVA I L A B L E AT B R O W N I N G . C O M OR CALL: ® 1-800-333-3288 BOSS ® OWNER'S MANUAL (BALLISTIC OPTIMIZING SHOOTING SYSTEM) Very important: Save this booklet. Carefully read this entire owner's manual before using your new Browning firearm. New Gun Owner's Record Keep this record for future reference: Browning Model __________________________________ Serial Number Purchase Price __________________________________ __________________________________ Gauge / Caliber __________________________________ Purchased From __________________________________ Date of Purchase __________________________________ YOU ARE RESPONSIBLE FOR FIREARMS SAFETY These are additional instructions specific to the BOSS® installed on your new A-Bolt or BAR rifle. You must read and understand the cautions and proper handling procedures outlined in this booklet and in the owner's manual received with your rifle before using your new BOSS®-equipped rifle. If you are missing the owner's manual for your rifle, we will send you a free replacement manual upon request. You can also visit our website at browning.com as many of our owner's manuals are posted on line. CAUTION: THE THREADING ON YOUR BARREL IS FOR BROWNING BOSS COMPONENTS ONLY. DO NOT INSTALL ANY OTHER DEVICE ONTO THE BROWNING BOSS BARREL. DO NOT INSTALL THE BOSS DEVICE ON ANY RIFLE, WHICH IS NOT DESIGNED AND FITTED FOR THE BOSS BY BROWNING. DOING SO MAY CAUSE SERIOUS INJURY OR DEATH TO YOURSELF OR OTHERS. ® ® ® ® G E N E R A L O P E R AT I O N The BOSS® (Ballistic Optimizing Shooting System) allows you to fine tune accuracy by modifying the vibrations of your rifle's barrel using an adjustable weight system. Every time a rifle is fired, barrel vibrations are set in motion. These vibrations occur in all directions, even back and forth along the axis of the barrel. Browning research has confirmed that barrel vibrations are the primary cause of inaccuracy. Barrel vibrations are influenced by many factors such as bullet type, bullet weight, primers, different powders and barrel configurations. The BOSS® adjusts timing of barrel vibrations so the bullet consistently leaves the rifle muzzle at the most advantageous time. Once the BOSS® is adjusted to this "Sweet Spot" for a given ammunition, your rifle will consistently deliver extraordinarily tight groups. With precision ammunition, BOSS®-equipped rifles of many calibers are capable of 100 yard, one hole groups. The smallest 3-shot group obtained during the BOSS® development measured an incredible .051" at 100 yards, using factory loaded ammunition. No 2 FIGURE 1 Micro Adjustable Lockout Body FIGURE 1A Micro Adjustable Lockout Body Micrometer Adjustment Ring Micrometer Adjustment Ring longer will you need to try a variety of ammunition to obtain acceptable accuracy. With the BOSS®, you can tune your rifle to get the optimum accuracy for all available factory loads. When adjusted to its Sweet Spot, the BOSS® will compensate for slight deviations in ammunition velocity. However, the BOSS® will not compensate for poor shooting or flyers caused by low quality bullets and ammunition. TO OBTAIN THE HIGHEST LEVEL OF ACCURACY FROM YOUR RIFLE, IT IS RECOMMENDED THAT THE RIFLE BORE BE CLEANED AFTER EVERY 12 TO 15 ROUNDS. SEE "CLEANING THE RIFLE BORE" SECTION OF THIS BOOKLET FOR CLEANING PROCEDURES. M U Z Z L E B R A K E F E AT U R E The BOSS® is available in two versions, the muzzle break version (Figure 1) and the CR (conventional recoil) version (Figure 1A). WARNING: THE BOSS WITH RECOIL REDUCING MUZZLE BRAKE PROVIDES SUBSTANTIAL INCREASED NOISE/MUZZLE BLAST. ALWAYS WEAR HEARING PROTECTION TO PREVENT HEARING LOSS OR DAMAGE. ® The unique exhaust hole pattern on the BOSS® with muzzle brake provides considerable recoil reduction. Recoil reduction of the BOSS® ranges from 30% to 50% - depending on caliber, weight of rifle, etc. You will experience an increase in noise and concussion (muzzle blast) when a BOSS®-equipped rifle is fired. Hearing protectors (shooting ear plugs or muffs) should always be worn to guard against hearing damage when shooting a BOSS®-equipped rifle. Wear shooting glasses 3 to protect your eyes from flying particles. Always keep a safe distance between the muzzle of your firearm and any persons nearby, as muzzle blast, debris and ejecting shells could inflict serious injury. BOSS ® S P E C I F I C AT I O N S The BOSS® body length is 2" for all calibers. The size of the gas vent holes and hole pattern is the same for all calibers. The size of the bullet exit hole is the same for all calibers except for the 338 Win. Mag. and 375 H&H. The thread system for the 338 Win. Mag. and the 375 H&H is different from other calibers to rule out the possibility of accidentally switching components and creating an unsafe combination. Do not attempt to interchange these systems. Use only the BOSS intended for use with your rifle. Each BOSS® consists of a micro-adjustable lock nut and body (Figure 1). The body of the BOSS® consists of a weight and muzzle brake. The weight and muzzle brake are affixed by LOCTITE®. The micro-adjustable lock nut has a micrometer adjustment ring. To obtain the utmost accuracy from your BOSS®-equipped rifle, it is very important that the micro-adjustable lock nut and body are always tight. THE "SWEET SPOT" Precision accuracy from the BOSS® system is achieved by calibrating your rifle caliber and ammunition with a prescribed Sweet Spot setting. (The Sweet Spot chart is available separately from this manual. If you do not have a Sweet Spot chart, call 1-800-333-3288 to request one. You can also look up this information at browning.com) This chart lists average, or suggested, Sweet Spots. These settings were determined through extensive testing by the Browning research and development staff. Sweet Spots may vary between rifles of identical specifications with given ammunition. Even one quarter of a turn away from the Sweet Spot can cause a group to spread out as much as one inch or more. We suggest you use our listed Sweet Spot settings as a starting point in determining the exact Sweet Spot setting for your particular rifle and make changes accordingly. NOTE: ANY CHANGE IN THE BOSS SETTING MAY SLIGHTLY ALTER YOUR RIFLE'S POINT OF IMPACT. ® 4 FIGURE 2 Calibrate the BOSS so "0" lines up with the hatch mark on the barrel. ® FIGURE 2A The micro-adjustable lock nut must be bottomed out. It is 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. On the Sweet Spot chart, Sweet Spots are listed by both ammunition and rifle model. Settings not listed, either do not apply or are for ammunition not yet tested. PRELIMINARY ADJUSTMENTS Before setting your Sweet Spot, it is important that your BOSS® be 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 initially determined. To find out if your BOSS® needs to be recalibrated, loosen the microadjustable lock nut 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 (Figure 2). If the "0" is not 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 lock nut so the "0" is aligned with the longitudinal hatch mark. To adjust the micrometer adjustment ring, insert your fingernail or a small pointed object in the split of the ring and rotate the ring (Figure 3). 5 FIGURE 3 Rotate the micrometer adjustment ring FIGURE 4 Full-turn Sweet Spot increments 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. SETTING YOUR RIFLE'S SWEET SPOT Full turn Sweet Spot settings or graduations are numbered 1-10 and inscribed on the barrel of your rifle (Figure 4). Smaller 1/10 turn increments are inscribed on the micrometer adjustment ring (Figure 5). To set the Sweet Spot, the micro-adjustable lock nut 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 lock nut indicates one full change in setting, or one index mark on the barrel. 1/10 turn increments are set by rotating the micro-adjustable lock nut 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 lock nut. The knurled portion of the microadjustable lock nut and micrometer adjustment ring must rotate together to ensure a precise Sweet Spot setting and retainment of proper calibration. 6 FIGURE 5 1/10 FIGURE 6 Example 1: Sweet Spot set at 6.0 turn Sweet Spot increments EXAMPLE 1 1 Suppose you have a 270 caliber A-Bolt rifle and are sighting in with 150 grain cartridges. Referring to the Sweet Spot chart, you will find the average Sweet Spot to be 6.0 for a 270 A-Bolt with 150 grain ammunition. 2 After having made sure your BOSS® is calibrated properly on the barrel, rotate the micro-adjustable lock nut counterclockwise six full revolutions. The edge of the micrometer adjustment ring should line up, or rest, on the marking for 6.0 on the barrel of the rifle. NOTE: It is not necessary to calibrate your BOSS® with each change in Sweet Spot settings. However, you should check the BOSS® periodically to assure proper alignment. 3 Since the Sweet Spot setting 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 (Figure 6). 4 Tighten the body of the BOSS® so it is secure against the microadjustable lock nut. 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 lock nut are tight (Figure 7). 7 FIGURE 7 Tighten the BOSS so it is secure FIGURE 8 Example 2: sweet spot set at 2.5 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 rifle and are using Federal 180 grain cartridges. Referring to the Sweet Spot chart, you will find the average Sweet Spot to be 2.5. 2 Calibrate your BOSS® and rotate the micro-adjustable lock nut counterclockwise until the edge of the micrometer adjustment ring lines up, or rests, on the marking for 2.0 on the barrel. 3 Since the Sweet Spot is listed as 2.5, the 5.0 inscribed on the micrometer adjustment ring should line up with the hatch mark or vertical line on the barrel (Figure 8). 4 Using the special wrench, tighten the body of the BOSS® so it is secure against the lock nut. Your BOSS® system is now calibrated for Federal 180 grain ammunition using a 300 Win. Mag. BAR rifle. MORE PRECISE ADJUSTMENTS If you desire to further experiment and possibly obtain even tighter groupings, turn the micro-adjustable lock nut 1/4 of a turn clockwise and fire your rifle at a safe target. If the group opens up (gets larger), turn the micro-adjustable lock nut counterclockwise and sight in at different 1/4 turns until you are satisfied with your groupings. Sweet Spot settings may vary between rifles of identical specifications with a 8 FIGURE 9 Barrel Mounting Screw FIGURE 10 Trigger Guard Screw BAR Forearm Locking Screw given ammunition. As in any sighting-in process, the best results are obtained through trial and error. You may need to retune the BOSS® should you decide to shoot ammunition of different brands, lots and/or types. Be sure to keep a record of your rifle's Sweet Spots, especially if you use your rifle for different game and shoot different loads. CAUTION: WHEN ADJUSTING THE SWEET SPOT, NEVER SET THE BOSS BEYOND THE 10 SETTING. ® With the BOSS® set beyond 10, it could become loose, misaligned or disengaged when firing the rifle. This could result in serious injury to yourself or others. IMPORTANT: Each time you set the Sweet Spot, the body of the BOSS® must be tight against the micro-adjustable lock nut. Failure to keep the components tightly locked will adversely affect accuracy. NOTE: The barrel mounting screw and trigger guard screw on the ABolt should also be fully tightened (Figure 9). If the barrel mounting scre ...