The BOSS™ and your Model 70: (Ballistic Optimizing Shooting System)
These are additional instructions specific to your BOSS™ equipped Model 70 rifle. Please read and understand the cautions and proper handling procedures outlined in this booklet and in your Model 70 owner’s manual, before using your new BOSS equipped rifle. If you are missing the operating manual for your rifle, we will send you a free manual on request.
Warning: The “BOSS” includes a recoil reducing muzzle brake which provides substantial increased noise/muzzle blast. Always wear hearing protection to prevent hearing loss or damage.
Caution: The threading on your barrel is for components for the U.S. Repeating Arms Co. BOSS only. Do not install any other device onto the Winchester Model 70 BOSS barrel. Do not install the BOSS device on any rifle which is not designed and fitted for the BOSS by U.S. Repeating Arms Co. Doing so may cause serious injury or death to yourself or others.
The Model 70 is considered by many to be the most perfectly designed rifle ever. The Model 70 is a rifle of history and unequaled modern performance — especially with the revolutionary BOSS. U.S. Repeating Arms Co. is excited to offer this incredible new patented technology on the Winchester Model 70.
The BOSS gives the Model 70 a degree of accuracy found only on expensive custom rifles. The Model 70 offers the rifleman the best of two worlds: traditional craftsmanship and the latest in modern rifle technology. Now, more than ever, it is truly “The Rifleman’s Rifle.”
How the BOSS™ Works
Barrel vibrations are the primary cause of rifle inaccuracy. 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. They are influenced by many factors such as bullet type, bullet weight, primers, different powders and even barrel configurations.
The BOSS (Ballistic Optimizing Shooting System) is an adjustable weight that alters rifle barrel vibrations. By adjusting the weight on the BOSS, you can tune your rifle to specific ammunition, allowing a bullet to consistently exit the rifle muzzle at the optimum point in barrel vibration. At this optimum point, either at the peak or valley of a vibration wave, the rifle barrel is momentarily motionless. The suggested “sweet spots” (found on a separate sheet supplied with this manual) are the starting points for determining the optimum accuracy of your BOSS-equipped Model 70. Once the true “sweet spot” is determined for a given ammunition, your rifle will consistently deliver extraordinarily tight groups. The BOSS allows you to tune your rifle to your ammunition to get the optimum accuracy for all available factory loads.
When adjusted to the “sweet spot,” the BOSS will compensate for slight deviations in ammunition velocity. The BOSS will not, however, 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 every 25 to 30 rounds. See “cleaning the rifle bore” section of this booklet for cleaning procedures.
Muzzle Brake Feature
The unique exhaust hole pattern on the BOSS 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 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.
The BOSS body length is 2 inches for most calibers. The size of the gas vent holes and hole pattern is the same for most calibers. The size of the bullet exit hole is the same for all calibers except for the 338 Win. Mag. The thread system for the 338 Win. Mag. is different from other calibers to rule out the possibility of accidentally or deliberately switching components and creating an unsafe
Warning: The .338 caliber BOSS has a larger exit bore than all other currently available calibers. Switching BOSS components from different calibers to the .338 barrel could cause a restriction or obstruction resulting in possible injury or death to the shooter or others.
Each BOSS consists of a micro-adjustable locknut and body. The body of the BOSS consists of a weight and muzzle brake. The weight and muzzle brake are affixed by LOCTITE®. To obtain the utmost accuracy from your BOSS equipped Model 70 it is very important that the micro-adjustable locknut and body are fully tightened before firing.
The “Sweet Spot”
Precision accuracy is achieved by calibrating your rifle caliber and ammunition with a “sweet spot” setting. The “sweet spots” for your Model 70 are found listed on a separate sheet supplied with this manual. If you are missing the “sweet spot” sheet or if there is no “sweet spot” listing for your rifle caliber or ammunition, go to the most current list of Sweet Spots settings now. “Sweet spot” settings were determined through extensive testing by U.S. Repeating Arms Co. 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 suggested “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.
Before adjusting your rifle to the “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 U.S. Repeating Arms Co. Research and Development when BOSS suggested “sweet spots” were determined.
To find out if your BOSS needs to be calibrated, loosen the micro-adjustable locknut 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 locknut, so that when bottomed out on the threads the “0” is aligned with the vertical hatch mark. To adjust the micrometer adjustment ring, insert your fingernail or a small pointed object in the split of the ring and simply rotate the ring .
Tuning your Rifle to the “Sweet Spot”
Full turn “sweet spot” setting or graduations are numbered 0-10 and inscribed on the barrel of your rifle. Smaller, 1/10 turn increments are inscribed at the rear of the locknut. To set the “sweet spot,” the micro-adjustable locknut is turned either clockwise or counterclockwise until it rests on the desired “sweet spot” number inscribed on your rifle’s barrel. One full revolution of the locknut indicates one full change in setting or one index mark on the barrel. 1/10 turn increments are set by turning the micro-adjustable locknut until the desired setting lines up with the longitudinal hatch mark on the barrel.
IMPORTANT: When adjusting the “sweet spot” make sure you grip the knurled surface of the micro-adjustable locknut. The knurled portion of the 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.
The suggested “sweet spots” for your Model 70 are listed on a separate sheet supplied with your manual. If you are missing the “sweet spot” sheet or if your rifle’s caliber or ammunition is not on the list, call U.S. Repeating Arms Co. at 1-800-782-4440.
Example 1 —
Suppose you have a 270 caliber Model 70 and are sighting in with 150 gr. cartridges. Referring to the “sweet spot” chart you will find the average “sweet spot” is 2.5 for a 270 caliber with 150 gr. ammo.
After having made sure your BOSS is calibrated, rotate the locknut counterclockwise two and one half full revolutions. The edge of locknut should line up or rest on the marking for 2 on the barrel.
NOTE: It is not necessary to calibrate your BOSS on the barrel with every change in “sweet spot” setting. However, you should check your BOSS periodically to assure that it is aligned.
Since the “sweet spot” is listed as 2.5, the 5 inscribed on the micrometer adjustment ring should line up with the hatch mark on the barrel.
Tighten the body of the BOSS so it is secure against the locknut. Use the special wrench supplied with your rifle.
Caution: Remove the wrench before firing your rifle.
Example 2 —
Suppose you have a 30-06 Sprg. Model 70 with 150 gr. cartridges. Referring to the “sweet spot” chart you will find the average “sweet spot” is 1.8.
Adjust your BOSS and rotate the micro-adjustable locknut counterclockwise until the edge of the locknut lines up or rests on the marking for 1 on the barrel.
Since the “sweet spot” is listed as 1.8, the 8 inscribed on the micrometer adjustment ring should line up with the hatch mark 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 150 gr. ammo for 30-06 Sprg.
More Precise Adjustments
If you desire to obtain even tighter groupings, turn the micro-adjustable locknut 1/4 of a turn clockwise from the “sweet spot,” and fire your rifle at your target. If groups open up, turn the locknut counterclockwise and shoot at different 1/4 turn settings until you are satisfied with your groupings. Again, “sweet spots” may vary between rifles of identical specifications with a given ammunition. As in any sighting-in process, best results are obtained through trial and error. You may need to retune the BOSS should you decide to shoot different brands, lots and types of ammunition.
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 on the barrel.
With the BOSS set beyond 10, the BOSS could become loose, misaligned or fall off 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 locknut. Failure to keep the components tightly locked will adversely affect accuracy.
NOTE: The action mounting screws on your Model 70 should be fully tightened. If the screws are loose, tighten the front screw first, then the rear trigger guard screw. Always leave the middle screw “snug, hand tight” only.
Care of your BOSS-Equipped Model 70
The BOSS is a precision instrument. IN ORDER FOR THE BOSS TO OPERATE EFFECTIVELY IT IS VERY IMPORTANT YOUR RIFLE REMAINS IN THE SAME CONDITION IT WAS PURCHASED. IT IS ABSOLUTELY NECESSARY FOR YOUR RIFLE’S BARREL TO REMAIN FREE-FLOATING AND PROPERLY BEDDED.
To check for adequate clearance, it is recommended that a piece of paper, folded once, be able to pass between the barrel and stock without any interference. If the barrel is not free-floating, take your rifle to a competent gunsmith or send it to U.S. Repeating Arms Co. Service Center. Special bedding of the action on your BOSS equipped Model 70 rifle is installed at the factory and aids greatly in improving accuracy. If you have any modifications done to your stock, make sure the bedding has not been altered. If the bedding on your rifle has been modified send your rifle to a U.S. Repeating Arms Co. Service Center.
Special Instructions on Cleaning the Rifle Bore
To maintain utmost accuracy from your BOSS equipped rifle, or any rifle, extensive testing has proven that the rifle bore must be cleaned every 25 to 30 rounds.
Caution: Before cleaning your rifle make certain your rifle is fully unloaded, the magazine is unloaded/removed, the safety is in the “on safe” position and your rifle is pointed in a safe direction.
We highly recommend that your rifle be cleaned with the BOSS installed on your barrel. Remove the bolt and clean from the breech end.
Modern cartridge jackets are made mainly of copper and zinc. These metals glide easier and increase barrel life, however, residues from copper and zinc also stick to the barrel and require more frequent cleaning. As top benchrest shooters have known for decades, copper solvent is the key to cleaning a barrel for optimum accuracy. The recommended cleaning procedure is as follows:
Clean the bore with a good powder solvent to remove all traces of powder residue. Performing this step before the application of a copper solvent will prevent the bore from refouling with copper so readily.
Swab the bore with a good copper solvent using the manufacturer’s recommended procedure. After neutralizing the solvent, generally with oil, it is important to swab the bore dry. Swabbing the bore dry will reduce copper buildup.
Note: Do not use solvents of different manufacturers concurrently. A chemical reaction may result that will corrode even stainless steel barrels. It is important to follow the manufacturer’s recommendations exactly.
If absolutely necessary, the BOSS may be removed to facilitate cleaning.
Clean the BOSS by removing the locknut and body from the rifle. With the components disassembled, wipe each component with oil. Lightly oil all threads and make sure exhaust holes on the body of the BOSS are free of obstructions.
Reassemble your BOSS by screwing on the micro-adjustable locknut then the BOSS body. After taking apart the BOSS it will be necessary to reset the “sweet spot” and it may be necessary to recalibrate the BOSS.
Make certain all cleaning patches are removed from the barrel and exhaust holes in the body of the BOSS before firing your rifle.
When firing for extreme accuracy, after cleaning the bore it is recommended two fouling shots be fired before shooting for accuracy. Additionally, it is recommended the rifle be allowed to cool every three rounds.
If your “Sweet Spot” listing card is missing from your owner’s manual please printout the most current Sweet Spots listing. If you would like more information regarding Winchester rifles or any of the fine Winchester products, please call the U.S. Repeating Arms Company Customer Service Department.
Suggested "Sweet Spots"
for Model 70 Rifles equipped with the BOSS Accuracy System*
WARNING: The “BOSS” includes a recoil reducing muzzle brake which provides substantial increased noise/muzzle blast. Always wear hearing protection to prevent hearing loss or damage.
Winchester Boss System
1 reply to this topic
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Re: Winchester Boss System
Posted 11 August 2004 - 08:55 AM
Admin... do you have a link to this info??? I need to order a manual for my rifle & boss...a nd the sweet spot card. Thanks a million for posting this!!