The rib at the muzzle end has two holes—one slightly higher than the other. Removing the pin and realigning the holes to the slot in the front rib post changes rib height at the muzzle. Your BT-99 Plus comes with the rib in the down position at the muzzle. With it in this position you have an approximate point of impact adjustment range from 6" to 12" above point of aim. If you desire to change the range to 3" to 9". or later return it to the original setting, perfonn the following:
NOTE: Although rarely necessary, at this point the rib itself is nearly ready to be removed entirely from the barrel. When performing point of impact adjustments only, it is never necessary to remove the rib. For a thorough cleaning of the rib adjustment mechanisms it may be helpful in some cases. See "Removing and Reinstalling the Rib," below, for instructions. Otherwise, proceed to step three for adjusting point of impact.
3 To set the front of the rib in the higher position, lift up on the rib until the lower hole in the rib lines up with the slot in the rib post (See Figure 21-A). To set the rib in the down position (as it comes from the factory) align the upper hole in the rib with the slot in the post. The rib is pushed all the way down onto the rib post in this position (See Figure 21-B). The amount of vertical change from one setting to the next may-seem small, but it results in an approximate 3" change in point of impact.
4 To secure your setting, insert the punch in one end of the roll pin and place the pin in the
Counterclockwise: raise point of impact.
Clockwise: lower point of impact.
the rear ot the rib up or down desired hole. Using a light hammer, tap the roll pin into position. Once in position, with no portion of the pin protruding from either side, the change is completed.
MAKING SMALL ADJUSTMENTS A T THE REAR OF THE RIB —
The rib is adjustable from the rear of the rib, in approximately 1/2" increments, by turning the rib elevator screw in or out. As you turn the screw you
will hear and feel a click. Kach click represents ap-
4 When your desired point of impact is achieved, the rib requires no further settings. The click mechanism is made to tightly hold point of impact at your desired setting.
5 Resetting the drop adjustment in the moveable cheek piece may be necessary whenever the plane of the rib is changed to alter the point of impact.
REMOVING AND REINSTALLING THE RIB —
It is never necessary to remove the rib for adjusting point of impact. To remove the rib for cleaning (if ever necessary), carefully perform the following to make sure no pans are marred or damaged:
1 Raise the rear of the rib by turning counterclockwise on the rear elevation screw until it is as high as it will go, as explained in step two under "Making Small Adjustments at the Rear of the Rib." Do not force.
2 Remove the roll pin at the front of the rib as explained in steps one and two under the sub-
proximately 1/2" adjustment in point of impact at 40 yards. You may use the screwdriver blade found on the Invector-Plus choke tube wrench (supplied) to make the adjustment.
1 To set a specific point of impact, first set the front rib position (if necessary) to the range of adjustment you will need (see above).
2 Insert the screwdriver end of the Invector-Plus tool into the rear elevation screw (See Figure 22). Then turn the screw fully down (if it is not already in that position). This will put point of impact at 6" above (with front of rib set down) or 3" above (with front of rib set up). It makes it easier to turn the screw in by pressing lightly down on the rib when lowering it.
3 Turn the screw out (counterclockwise) to raise point of impact. Remember, each click represents 1/2" movement. Turning the screw in (clockwise) lowers point of impact. Do not force the screw after reaching its maximum up/down travel.
heading ' Changing the Position of the Rib at the Muzzle End."
3 Lift up on the muzzle end of the rib about 30°. Carefully lift the rib forward and out from the rear rib elevator housing. Never attempt to remove the rib by lifting on the front of the rib without the rear rib adjustment fully raised.
4 With the rib removed be careful not to lose the rib pivot. It is the circular part with a shoulder on each side that is fitted into the rib. It is easily removed and reinserted.
5 Removing the rib exposes the elevator detent spring which is inserted large end first into the groove in the rear rib elevator housing, with the bend facing up. It is unnecessary to remove this spring. Clean and lightly oil all rib components as necessary.
6 To reinstall, make sure the elevator detent spring is installed properly and the elevation screw is turned fully counterclockwise. Insert the rear of the rib into the rib elevator housing with the front of the rib up about 30 degrees. Make sure that the shoulders on the rib pivot are aligned with the grooves in the rear rib elevator housing. Lower the front of the rib down onto the front rib post and secure the front of the rib with the pin at the appropriate setting as explained previously.
Optional Barrel Porting_
Your gun may or may not have optional barrel porting. The drilled holes in the top of the barrel are desired by some shooters for their tendency to reduce barrel jump and give a feeling of lower recoil against the face. They require only an occasional cleaning as described under "Cleaning Suggestions' later in this manual.
Invector-Plus Choke Tube System_
Your BT-99 Plus is provided with the Invector-Plus screw in choke tube system. You can confirm this by reading the inscription on the right side of the barrel. The words INVECTOR-PLUS mean your shotgun uses a choke tube system designed for use in
DO NOT USE BROWNING INVECTOR CHOKE TUBES IN ANY SHOTGUN BARRELS NOT SUPPLIED BY BROWNING. ALSO, DO NOT USE ANY OTHER CHOKING DEVICE IN ANY SHOTGUN BARRELS SUPPLIED BY BROWNING. USE ONLY THE APPROPRIATE GAUGE AND TYPE OF CHOKE TUBES MARKED INVECTOR-PLUS.
CAUTION: WHENEVER HANDLING ANY SHOTGUN FOR THE PURPOSE OF REMOVING OR INSTALLING A CHOKING DEVICE, MAKE ABSOLUTELY CERTAIN THE GUN IS FULLY UNLOADED, AND THE ACTION IS BROKEN OPEN! NEVER ATTEMPT TO REMOVE OR INSTALL A SHOTGUN CHOKING DEVICE ON A LOADED FIREARM!
1 Fully unload your BT-99.
ALWAYS UNLOAD YOUR SHOTGUN — FULLY. INSPECT THE CHAMBER TO MAKE SURE IT DOES NOT CONTAIN ANY SHELLS.
Browning 12 gauge shotguns with back-bored barrels. The extra length, combined with special tube tapers, gives you the finest possible patterns for target shooters. Plus, you retain the same choke switching convenience of the standard Invector system. Invector-Plus Tubes are fully steel and lead shot compatible. A special "Plus" choke tube wrench is provided to remove and tighten these tubes. This wrench also has a screwdriver end for performing rib adjustments.
CAUTION: Invector-Plus tubes are for use in Browning shotguns with Browning back-bored barrels only (.745" + 0 - .005), and are not interchangeable with regular 12 gauge Invector choke tubes. Do not use Invector-Plus tubes in barrels threaded for standard Invector tubes. Do not use standard Invector tite in barrels threaded for Invector-Plus tubes. Failure to follow these warnings may cause damage to your gun and cause injury to yourself and others.
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