Mossberg 500, 835, 590 Pump Action Shotgun Instructions Manual

							9
Move the forearm/action slide assembly rearward so that the bolt assembly and bolt slide are
three quarters of the way rearward. When the bottom of the bolt slide is aligned with the
clearance cuts in the sides of the receiver, lift the bolt slide upward and out of the receiver
(Fig. 10).
Remove the bolt assembly by sliding it forward and out of the receiver assembly through the
barrel opening at the front of the receiver (Fig. 11-A).
NOTE: The safety button located on the upper rear of the receiver must be fully rearward
in the “ON” (SAFE) position to remove the elevator assembly (Fig.2).
Pivot the front portion of the elevator upward out of the receiver (Fig. 11-B). Squeeze the two
arms which form the open end of the elevator assembly together sufficiently to disengage and
remove the elevator from the receiver (Fig. 11-C).     
						

							10
Remove the forearm/action slide assembly by sliding it forward and off the magazine tube.
CAUTION: Field disassembly is now complete! The shotgun should not be
disassembled further for routine cleaning or maintenance. Further disassembly should
only be performed at the factory or by a qualified gunsmith.
CLEANING AND LUBRICATION
With proper care, your Mossberg
® shotgun will  provide you with years of dependable service.
Your firearm should be inspected and cleaned periodically to insure that it remains in good
condition. Clean your firearm as soon as possible after use. This is especially important if your
firearm has been exposed to moisture.
Use the instructions and equipment provided in a quality gun cleaning kit.
For maximum performance and continued satisfaction with your shotgun, periodic cleaning
and lubrication are essential. Always be sure that the safety button is fully rearward in the “ON”
(SAFE) posiition (Fig. 2) and that the firearm is unloaded before cleaning or lubricating your
shotgun. Wear eye protection during cleaning.
Normal use requires only that the mechanisms be free of excessive shooting residue. Very little
lubrication other than a light oiling of external surfaces to prevent rust is needed.
If the shotgun is to be stored for a long period of time it should be thoroughly cleaned and oiled.
Do not plug barrel or store in a fabric lined case that will absorb  lubricant from the shotgun.
Scrub bore and chamber with solvent and follow with cleaning patches until barrel is clean. A
final pass with a lightly oiled patch will provide a protective coating. Clean and remove any
deposits in the barrel extension.
All metal parts should be cleaned with gun solvent and lightly lubricated with gun oil. Over
lubrication should be avoided. Use only lubricants specifically designed for firearms. Avoid the
use of abrasives which may damage the metal finish.
Make sure the barrel is free of obstructions and excessive lubricant after
cleaning.
Camo guns: Caution should be exercised to avoid exposure of camouflage pattern to strong
solvents.
BOLT AND TRIGGER HOUSING ASSEMBLIES
The bolt and trigger housing assemblies are complex assemblies and should not be
disassembled except by the factory or qualified gunsmith.
Clean as complete assemblies with gun solvent and lightly lubricate with gun oil.
ASSEMBLY OF INTERNAL RECEIVER COMPONENTS
Place the receiver with the trigger housing opening upward on a clean surface.
Check to be certain that the safety button on the top rear of the receiver is fully rearward in the
“ON” (SAFE) position (Fig. 2). Slide the forearm assembly onto the magazine tube while guiding
the action slide bars into the corresponding cuts in the front of the receiver (Fig. 12). 
						

							11
Assemble the elevator by squeezing the arms together sufficiently to position them in the
receiver so that the buttons on the elevator fit into the corresponding (1/4 [6.4 mm]) diameter
holes in the receiver (Fig. 11).
Pivot the elevator so that the forward portion of the elevator is even with the outside edge of the
cavity in the receiver.
Insert the rear of the bolt assembly, with its bolt lock downwards toward the front inside top of the
receiver, into the barrel opening of the receiver. Depress the ejector (located in the side of
the receiver opposite the ejection port) to allow the bolt assembly to slide fully rearward into the
receiver.
The ejector must fit into the corresponding slot in the bolt (Fig. 11).
Push the elevator down until it rests against the bolt. Position the rear of the bolt assembly even
with the rear of the clearance cuts in the sides of the receiver (Fig. 13-B).
Position action bars so the notch on the bar is even with the cuts on the inside receiver walls
(Fig. 13-A).
The bolt slide should be positioned with the slotted side facing up, with notch to the rear (Fig. 13).
Assemble the bolt slide, lowering the front of the bolt slide first. The bolt slide protrusion fits into
the corresponding cut on the bottom of the bolt lock and action bar slots (Fig. 13-C).
Hold the bolt slide down and pull the forearm assembly forward. The bolt and bolt slide should
move freely in their cuts in the receiver. If parts do not slide easily – DO NOT FORCE –
disassemble and reassemble, paying attention to the relationship of the bolt, bolt slide and
action slide bars.
Position the cartridge stop and cartridge interrupter in their proper places on the inside walls of
the receiver (Fig. 9).
The hooks must face inward toward the center of the cavity away from the receiver walls.     
						

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TRIGGER HOUSING ASSEMBLY INSTALLATION
NOTE:Hammer must be in the fully-cocked position to allow the trigger housing to be
inserted in the receiver.
Hold the cartridge stop and cartridge interrupter in place firmly against the receiver walls with
one hand and grasp the trigger housing assembly with the other (Fig. 9).
Insert the lugs, on each side of the front corner of the trigger housing into the slots on each side
of the receiver (Fig. 14-A), then ease the rear of the housing assembly down and into position
(Fig. 14-B). DO NOT FORCE!
NOTE: If the trigger housing does not fit into place easily, check that all internal trigger housing
pins are flush with the side of the housing and that the cartridge interrupter and cartridge
stop are positioned properly.
Align the trigger pin hole in the housing asembly with those in the receiver. Insert the trigger
housing pin and push in fully until flush with the side of the receiver (Fig. 14).
FUNCTION TESTING
AFTER PERFORMING ANY WORK ON YOUR FIREARM SUCH AS CLEANING,
DISASSEMBLY OR INSTALLATION OF AN ACCESSORY:
a. Move the safety button fully rearward to the  “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and physically check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
Depress and hold the action lock lever (Fig. 3). Open and close the action several times to check
for free movement of the action assembly.
Close the acton (forearm fully forward) and leave the safety in the “ON” (SAFE) position. Pull the
trigger rearward fully. The hammer should not fall (No Fire).
Remove your finger from the trigger. Move the safety to the “OFF” (FIRE) position.The hammer
should not fall (No Fire).
Leave the safety in the “OFF” (FIRE) position.
Pull the trigger rearward. The hammer should fall (Fire).
Open the action by moving the forearm fully rearward. Move the safety fully rearward to the “ON”
(SAFE) position.   
						

							IF YOUR FIREARM DOES NOT PERFORM AS DESCRIBED IN ANY OF THE
ABOVE STEPS, CONTACT O.F. MOSSBERG & SONS, INC., IMMEDIATELY.
DO NOT ATTEMPT TO USE THE FIREARM.
SIGHT ADJUSTMENTS
BEFORE MAKING ANY SIGHT ADJUSTMENTS:
a. Move the safety button fully rearward to the  “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and physically check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
RIFLE SIGHT ADJUSTMENTS
IRON SIGHTS:
Elevation may be adjusted by loosening the small screw in the center of the rear sight leaf. This
will allow the sight blade to be moved upward or downward as required.
Windage may be adjusted by moving the rear sight base to the left or right in the dovetail slot in
the barrel. Place a wooden dowel or other object that will not damage the finish, against the side
of the sight base. Tap the dowel with a hammer until the desired sight location is achieved.
Remember: Move the rear sight in the same direction you would like the shot to move. For
example, if the point of impact is low and left at the point of aim, move the rear sight upward and
to the right.
GHOST RING
® SIGHT ADJUSTMENTS
13
Williams Style rear sight:
Elevation may be adjusted by loosening the smaller of the two screws on the rear sight leaf
base. This will allow the sight leaf base to be raised or lowered by sliding the base up or down the
rear sight ramp. Tighten screw after adjustment.
Windage may be adjusted by loosening the larger of the two screws and sliding the sight leaf left
or right in the sight leaf base. Tighten screw after adjustment.
Remember: Move the rear sight in the same direction you would like the shot to move. For
example, if the point of impact is low and left of the point of aim, move the rear sight upward and
to the right.   
						

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MOSSBERG ACCESSORY BARRELS
Accessory barrels are interchangeable only within specific model, gauge and
magazine capacity.
500
® Models:HS410 barrels are not interchangeable with standard Model 500 .410 bore
sporting barrels.
PISTOL GRIP INSTALLATION
BEFORE PERFORMING ANY DISASSEMBLY OR ASSEMBLY PROCEDURE:
a. Move the safety button fully rearward to the  “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and phsycially check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
To Remove Buttstock:
1) Loosen the top screw holding the recoil pad or buttplate on stock. Note: Most models use
Phillips head screws.
2) Loosen and 
remove the bottom recoil pad or buttplate screw.
3) Swing the recoil pad or buttplate around the top screw which will allow access to the stock
bolt through the stock butt hole.
4) Check stock bolt head configuration. Some models use a slotted head,others use a 1/2 in.
hex head.
5) Loosen and remove stock bolt by turning it counterclockwise. The stock may now be
removed from the receiver.
Installation of Pistol Grip:
1) Align mounting hole in pistol grip with threaded hole in rear of the receiver.
2) Slip washers on bolt. Insert bolt through pistol grip into hole in receiver. Finger tighten bolt
to insure threads are properly engaged. If you encounter difficulty, unscrew both and
repeat procedure.
3) Using Allen wrench supplied, tighten bolt very snugly.
Upon firing, recoil force will cause the shotgun to move rearward and upward. Never
hold the shotgun at eye level and attempt to sight down the barrel. To avoid possible
injury, grip the shotgun securely with one hand on the forearm and one hand on the
pistol grip. Pistol grip models are designed to be held at waist level when firing.
Fig. 16   
						

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SPEEDFEED STOCK
BEFORE CLEANING OR REMOVING THE SPEEDFEED STOCK:
a.    Move the safety button fully rearward to the “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and physically check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
The stock springs and followers should be removed periodically and the tube and
parts cleaned to remove debris. Do not lubricate these parts.
The recoil pad on the speedfeed stock is under spring pressure. Remove rounds from
storage tubes to minimize the spring pressure. Use caution when removing recoil pad
screws to prevent injury to yourself or others around you.
a)     Loose and  remove the two recoil pad screws by turning  them  counterclockwise.
b)     Remove recoil pad, springs and plastic followers. Place on a clean dry surface.
TO REASSEMBLE
1) Insert one plastic follower into each magazine tube in the stock. Be sure the hollow portion
of the follower is facing toward the rear of the stock.
2) Insert one spring in each of the two magazine tubes. The springs will fit inside the cupped
end of the followers inserted in the previous step.
3) Screw the recoil pad screws into the recoil pad until the screw points come through the
opposite side about 1/8 of an inch. Place the pad against the springs so that the end of
each spring rests against the recessed area on the pad.
4) Compress the springs into the tubes by pushing the pad flush against the stock. Adjust the
pad until you feel the points of the screws fit into the pre-drilled holes in the stock.
5) While maintaining pressure on the pad, tighten the recoil pad screws securely. Do not
overtighten screws.
6) Check for free movement of the followers by pushing them into the magazine tube with
your finger and allowing them to snap back into position under spring pressure.
HEAT SHIELD
BEFORE PERFORMING ANY DISASSEMBLY OR ASSEMBLY PROCEDURE:
a. Move the safety button fully rearward to the “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and physically check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
HEAT SHIELD INSTALLATION
NOTE: The heat shield can only be installed on 12 ga., plain barrel models. Heat shield will
not fit on barrels with Ghost Ring
® sights.
1) Follow barrel removal procedures as described in this Owner’s Manual. 
						

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2) Carefully remove front sight by turning it counterclockwise. Take precautions to insure you
do not damage the barrel finish.
3) Slide heat shield onto barrel from muzzle end. Large ring on heat shield is positioned
towards rear of barrel.
4) With the heat shield on the barrel, use a small padded “C” clamp or a vise, to close the
forward clamp of the heat shield.
5) Position the appropriate length plastic spacer or optional bushing style spacers between
the forward clamp. Insert the two screws and start the two hex nuts on the screws using a
7/64 hex key wrench and a 5/16 open end or box wrench. DO NOT FULLY TIGHTEN
THE TWO SCREWS YET (Fig. 17).
6) Reassemble barrel to action.
When securing heat shield, barrel must be attached to shotgun. Barrels with heat
shield secured are not interchangeable without proper refitting of heat shield to gun as
described in the above procedure.
Make sure takedown screw is secure and the barrel is fully seated before proceeding to the next
step.
7) Position  heat shield  so  that  the rear (large ring) butts up against the front of the receiver.
8) Using a 7/64 Allen wrench and a 5/16 open end or box wrench, tighten the clamp screws
to securely hold the heat shield in place. DO NOT OVERTIGHTEN THE SCREWS.
9) Reinstall front sight.
Whenever the heat shield barrel is removed from the shotgun, repeat the above steps
5-8 to insure that the shield is not preventing the barrel from being seated fully.
DUAL - COMB® TROPHY STOCK
BEFORE PERFORMING ANY DISASSEMBLY OR ASSEMBLY PROCEDURE:
a. Move the safety button fully rearward to the  “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and physically check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
500® AND 590® MODELS 6-SHOT CUT AT 1 5/16 (A)
590 MODELS WITH BAYONET LUG CUT AT  1 7/8 (B)
590 MODELS WITHOUT BAYONET LUG, USE AS IS.   
						

							To Change Removable Combs:
1) Using a 3/16 inch Allen head wrench (supplied) unscrew and remove the comb retaining
screw found at the top center of the removable comb.
2) Place the desired comb into position. Insert the comb retaining screw and snug-tighten.
Do not overtighten as this will damage the internal assembly components.
ACCU, ACCU-STEEL, ACCU-MAG CHOKE TUBES
BEFORE REMOVING OR INSTALLING ANY CHOKE TUBE:
a. Move the safety button fully rearward to the  “ON” (SAFE) position and keep
muzzle pointed in a safe direction.
b. Open the action, visually and physically check chamber, elevator and magazine
tube to be certain the firearm is unloaded.
Do not use bent or deformed tubes as these may result in tube or barrel damage upon
firing. Inspect tubes periodically as to insure they are properly installed and in good
condiiton. Pay special attention to the threaded end of the tube to be certain it is not
deformed or dented.
Never fire the shotgun without a choke tube properly installed. Failure to do so will
damage the precision threads on the inside of the barrel.
CARE & CLEANING: The precision threads on your choke tube should be kept clean and lightly
oiled at all times.
During cleaning of the barrel, be certain a choke tube is properly installed. This will avoid residue
build-up on threads.
Extra-Full choke tubes are not recommended for use with buckshot or slugs.
The “Improved Cylinder” choke tube will usually produce the best accuracy with most slugs.
ACCU CHOKE TUBES
ACCU-CHOKE TUBES - are designed for Best Lead Shot Patterns. STEEL SHOT
can be fired through Accu-choke tubes however, better steel shot patterns may be
obtained by using ACCU-STEEL choke tubes.
To  remove choke tube, loosen it with the choke wrench provided, turning counterclockwise.
When loose, remove completely with fingers, put choke on a clean dry surface.
To  install choke tube, first screw the tube clockwise into barrel by hand and then tighten the tube
until snug with a choke wrench. Do not use excessive force when installing. Tube tightness
should be checked periodically. Accu tubes fit competely inside the muzzle of the barrel when
fully installed.
ACCU CHOKE TUBES
GAUGE ITEM # LEAD SHOT  PATTERNS
12 95190 Full
12 95195 Modified
12 95200 Imp. Cylinder
20 95215 Full
20 95220 Modified
20 95225 Imp. Cylinder
12 95235 Skeet
12 95267 XX Full (Turkey Tube)
12 95245 Improved Modified
17 
						

							ACCU-STEEL CHOKE TUBES
ACCU-STEEL TUBES - have been specifically designed for exceptional endurance and
controlled patterning of steel shot.
These tubes should provide the best pattern results for the steel shot sizes stamped on each
tube.
Lead shot may be used with ACCU-STEEL tubes; however, pattern tests should be made to
compare the pattern change.
To  remove choke tube, loosen with the choke wrech provided, turning counterclockwise. When
loose, remove completely with fingers, put choke on a clean dry surface.
To  install choke tube, first screw the tube clockwise into barrel by hand and then tighten the tube
until snug with a choke wrench. Do not use excessive force when installing. Tube tightness
should be checked periodically.
ACCU-STEEL tubes protrude beyond the muzzle and are designed specifically for steel shot.
Choke designations are marked on each tube for specific steel shot sizes.
ACCU-STEEL CHOKE TUBES
GAUGE ITEM # STEEL SHOT  PATTERNS
12 95110 Full for T,F,BB,#1,2
12 95115 Full for #4,6
12 95117 Extra-Full for T,F,BB,#1,2
12 95120 Modified for All Steel Shot Sizes
20 95125 Full for #4,6
20 95130 Modified for All Steel Shot Sizes
ACCU-MAG CHOKE TUBES
(835 MODELS ONLY)
ACCU-MAG choke tubes are internal, flush fitting choke tubes designed for use with LEAD,
STEEL shot.  Each durable tube is clearly marked, as a guide, with the lead and the steel shot
pattern it will produce.
To  remove  a choke tube from the muzzle of the barrel, loosen with the choke wrench provided,
turning it counterclockwise. When choke tube is loosened, remove it completely with fingers.
Put choke tube on a clean, dry surface.
To  install choke tube, screw the tube clockwise into barrel by hand and then tighten the
tube until snug with choke wrench. These tubes fit competely inside the barrel when
properly  installed. Do not use excessive force when installing. Tube tightness should be checked
periodically.
12 GA. MODEL 835 ACCU-MAG CHOKE TUBES
ITEM # LEAD SHOT  PATTERN* YDS STEEL SHOT PATTERN YDS
95256 Skeet 40 Skeet 40
95252 Imp. Cyl. 40 Mod. T&F 40
95253 Modified 40 Mod. #2 & BB 40
95254 Full 40 Full, #2 & BB 40
95255 Extra Full T&F 40
95257 Ulti-Full 30
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