Mossberg 500 / 590

Manufacturer’s video: Loading and Unloading - Mossberg 500 / 590 Series Shotguns MOSSBERG

1. Point the muzzle in a safe direction and keep your finger off the trigger.
2. Move the safety button fully rearward to the ON (safe) position.
3. Depress the action lock lever on the left side behind the trigger guard and pull the forearm rearward to open the action.
   Removed at this step: Chambered shell, if present
4. Cycle the action repeatedly, catching each shell as it ejects, until no more shells feed from the magazine tube.
5. With the action open, visually and physically check the chamber, the elevator, and the magazine tube.
   WarningThree places, not two. The manual names the chamber, the elevator, and the magazine tube specifically.
6. Remove all live ammunition from the work area, and put on eye protection before going further.

Barrel and trigger housing. Verified against the factory manual — note the bolt-position step before the barrel comes off, and that the barrel rotates out rather than pulling straight.

1. Complete the Clear and Make Safe procedure and put on eye protection.
2. Depress the action lock lever and open the action by sliding the forearm fully rearward.
3. Move the forearm slowly forward from the fully rearward position until the front of the bolt sits in the middle of the ejection port.
   WarningDo not skip this. The barrel will not come out cleanly unless the bolt is positioned here first.
   TipThis is the step most commonly left out of informal instructions for this shotgun.
4. On a 590 or 835, unscrew the magazine cap counterclockwise. On a 500, 505, 510 or 535, loosen the takedown screw counterclockwise until its threads are completely disengaged from the end of the magazine tube.
   WarningOn 590 and 835 models the magazine spring retainer and spring are under significant spring pressure.
   Removed at this step: Magazine cap or takedown screw
5. Remove the barrel from the receiver with a gentle back-and-forth rotational movement while pulling it out of the receiver assembly.
   TipRotate as you pull. Pulling straight out is the common mistake.
   Removed at this step: Barrel
6. Position the shotgun on a clean surface with the trigger guard upward.
7. Using a punch no greater than 3/16 in (4.76 mm) in diameter, push out the small-diameter trigger housing retainer pin from the side of the receiver, roughly 1/2 in (12.7 mm) below the rear of the trigger guard.
   Removed at this step: Trigger housing retainer pin
8. Remove the trigger housing assembly by lifting the rear portion upward first.
   WarningOnce the trigger housing is out of the receiver, do not pull the trigger and let the hammer fall. The manual warns this can injure you and damage the assembly.
   Removed at this step: Trigger housing assembly
9. Stop here for routine cleaning. The trigger housing assembly itself must not be disassembled — the manual restricts that to an authorised service centre or a qualified gunsmith.

Beyond routine cleaning. Study how the parts sit before removing them — they must go back in the same relationship.

1. Complete the field strip, with the trigger housing assembly removed.
   WarningBefore going further, study how the internal components are arranged inside the receiver. The manual asks for this explicitly.
2. Remove the cartridge interrupter and cartridge stop from the receiver.
   TipIt may be necessary to tap the sides of the receiver lightly to release these parts. On left-hand models they sit in the same positions but the ejection port is on the opposite side.
   Removed at this step: Cartridge interrupter Cartridge stop
3. Move the forearm and action slide assembly rearward until the bolt assembly and bolt slide are three quarters of the way rearward.
   WarningPay attention to the position of the bolt, bolt slide, and action slide bar assembly — they must be in the same relationship on reassembly.
4. When the bottom of the bolt slide aligns with the clearance cuts in the sides of the receiver, lift the bolt slide upward and out of the receiver.
   Removed at this step: Bolt slide
5. Remove the bolt assembly by sliding it forward and out of the receiver through the barrel opening at the front.
   Removed at this step: Bolt assembly
6. With the safety button fully rearward in the ON position, pivot the front portion of the elevator upward out of the receiver and squeeze its arms together to free it.
   WarningThe safety must be fully rearward in the ON position for the elevator assembly to come out.
   Removed at this step: Elevator

Removes the slide tube nut with the fabricated tube nut tool, then slides the slide grip and anti-rattle spring off the action slide assembly (WP 0023 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0023 00, p. 0023 00-1 archive.org [3]

1. Remove the barrel and take the fore end assembly off the receiver (operator field strip, WP 0014 00).
2. Unscrew the slide tube nut from the action slide assembly with the tube nut tool.
   TipThe tube nut tool is a manufactured item; WP 0030 00, Figure 1 gives its dimensions (1080 bar stock).
   Removed at this step: Slide tube nut
3. Remove the slide grip and the anti-rattle spring from the action slide assembly.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
   Removed at this step: Shotgun slide grip Anti-rattle spring

Removes the parts attached to the barrel: the Model 590's heat shield, the front sight, the Model 500's retaining ring and machine screw, and (only if damaged) the sling swivel (WP 0024 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F). A bent barrel goes to direct support.

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0024 00, p. 0024 00-1 archive.org [3]

1. Field strip the shotgun and remove the barrel (WP 0014 00).
2. On the Model 590, remove the two self-locking nuts, the two screws, the heat shield spacer and the heat shield from the barrel.
   TipDiscard the self-locking nuts; new ones are used on assembly.
   Removed at this step: Self-locking nuts (2) Screws (2) Heat shield spacer Heat shield
3. Remove the front sight from the barrel.
   Removed at this step: Front sight
4. On the Model 500, remove the retaining ring and the machine screw from the barrel.
   Removed at this step: Retaining ring Machine screw
5. Remove the sling swivel only if it is damaged. On an old-style swivel, remove the screw, the swivel and the sleeve bushing.
   Removed at this step: Screw Swivel Sleeve bushing
6. On a new-style swivel, turn the locking knob fully counterclockwise.
   TipRemoval of the old and new swivel is the same for both models.
7. Push in on the locking knob to release the swivel-locking bar and remove the sling swivel from the swivel post.
   Removed at this step: Sling swivel
8. Turn the swivel post counterclockwise to remove it.
   Removed at this step: Swivel post

Takes off the recoil pad, then removes the stock bolt (machine screw) with its washer and lock-washer to separate the stock (military shoulder stock P/N 14762MIL) from the receiver; the sling swivel comes off only if damaged (WP 0025 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0025 00, p. 0025 00-1 archive.org [3]

1. Remove the two machine screws and the recoil pad from the stock.
   Removed at this step: Machine screws (2) Recoil pad
2. Remove the machine screw, washer and lock-washer from inside the stock.
   TipDiscard the lock-washer; a new one (P/N 7615P) is used on assembly.
   Removed at this step: Machine screw (stock bolt) Washer Lock-washer
3. Separate the stock from the receiver.
   Removed at this step: Stock
4. Remove the sling swivel only if it is damaged. On an old-style swivel, remove the screw and the swivel, and on the Model 500 also the sleeve bushing and swivel washer.
   Removed at this step: Screw Swivel Sleeve bushing Swivel washer
5. On a new-style swivel, turn the locking knob fully counterclockwise, push it in to release the swivel-locking bar, and remove the sling swivel from the swivel post.
   Removed at this step: Sling swivel
6. Turn the swivel post counterclockwise to remove it.
   Removed at this step: Swivel post

Removes the hex screw, washer and lock-washer holding the pistol grip assembly to the receiver, and the swivel post (WP 0026 00). The pistol grip is an Additional Authorization List item that replaces the shoulder stock; remove the stock first per WP 0025 00. The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Applies to: Military pistol grip assembly P/N 7995P (AAL item)

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0026 00, p. 0026 00-1 archive.org [3]

1. Field strip the shotgun (WP 0014 00).
2. Remove the hex screw, washer and lock-washer from the pistol grip.
   TipDiscard the lock-washer; a new one (P/N 7613P) is used on assembly.
   Removed at this step: Hex screw Washer Lock-washer Pistol grip
3. Remove the swivel post.
   Removed at this step: Swivel post

On the Model 590, takes the magazine catch retainer, spring and follower out of the tube, and unscrews the tube from the receiver only if it must be replaced. On the Model 500 the tube is unscrewed from the receiver with a strap wrench first, then the follower and spring come out. Direct support maintenance (Chapter 4, WP 0028 00; MAC Repair at F).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0028 00, pp. 0028 00-1 to 0028 00-2 archive.org [3]

1. Remove the barrel assembly and the fore end assembly (WP 0014 00).
2. Model 590: remove the magazine catch retainer, the magazine spring and the cartridge follower from the magazine tube.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
   Removed at this step: Magazine catch retainer Magazine spring Cartridge follower
3. Wrap a wiping rag around the receiver and clamp it in a bench vise with jaw caps, closing the vise just enough to hold it.
   TipOn the Model 590 do this and the next two steps only if the magazine tube must be replaced. On the Model 500 they come first, because the follower and spring come out after the tube is off.
4. Place a strap-style pipe wrench around the magazine tube and turn it to the left (counterclockwise) to loosen it.
5. Remove the magazine tube from the receiver.
   Removed at this step: Magazine tube assembly
6. Model 500: remove the cartridge follower and the magazine spring from the magazine tube.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
   Removed at this step: Cartridge follower Magazine spring

Drives out the bolt lock pin to free the bolt lock, removes both extractors with their pins and springs, then the firing pin retaining pin, firing pin, washer and spring. Direct support maintenance (Chapter 4, WP 0029 00; the MAC lists Replace of the bolt assembly at F), with the small arms repairman tool kit and the basic small arms shop set.

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0029 00, p. 0029 00-1 archive.org [3]

1. Field strip the shotgun and remove the bolt (WP 0014 00).
2. Remove the grooved headless pin and the bolt lock from the bolt.
   Removed at this step: Grooved headless pin (bolt lock pin) Bolt lock
3. Remove the two cartridge extractor pins, the left-hand and right-hand cartridge extractors, and the two extractor springs from the bolt.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
   Removed at this step: Cartridge extractor pins (2) Left-hand cartridge extractor Right-hand cartridge extractor Cartridge extractor springs (2)
4. Remove the firing pin retaining pin, the firing pin, the flat washer and the spring from the bolt.
   TipWP 0029 00 calls this spring the 'follower spring'; the parts list (WP 0040 00, item 9) names it SPRING, FIRING PIN.
   Removed at this step: Firing pin retaining pin Firing pin Flat washer Firing pin spring

Slides the slide grip back onto the action slide assembly, fits the anti-rattle spring and tightens the slide tube nut with the tube nut tool (WP 0023 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0023 00, p. 0023 00-1 archive.org [3]

1. Slide the slide grip onto the action slide assembly.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
2. Install the anti-rattle spring.
3. Screw the slide tube nut onto the action slide assembly and tighten it with the tube nut tool.

Installs a new-style sling swivel, the front sight, the Model 590 heat shield with new self-locking nuts, and the Model 500 retaining ring and machine screw (WP 0024 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0024 00, p. 0024 00-4 archive.org [3]

1. Install the swivel post by turning it clockwise.
   TipIf an old-style swivel was removed, replace it with the new-style swivel.
2. Turn the locking knob fully counterclockwise.
3. Push in on the locking knob to release the swivel-locking bar and insert the bar through the swivel post.
4. Tighten the locking knob by turning it fully clockwise.
5. Install the front sight on the barrel.
6. On the Model 590, install the heat shield, the heat shield spacer, the two screws and two new self-locking nuts on the barrel.
7. On the Model 500, install the retaining ring and the machine screw on the barrel.

Refits the sling swivel, then bolts the stock to the receiver with the machine screw, washer and a new lock-washer, and refits the recoil pad (WP 0025 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0025 00, p. 0025 00-4 archive.org [3]

1. Install the swivel post by turning it clockwise.
   TipIf an old-style swivel was removed, replace it with the new-style swivel.
2. Turn the locking knob fully counterclockwise, push it in to release the swivel-locking bar, and insert the bar through the swivel post.
3. Tighten the locking knob by turning it fully clockwise.
4. Align the stock with the receiver assembly.
5. Place the washer and a new lock-washer on the shaft of the machine screw.
6. Insert the machine screw into the end of the stock and tighten it into the receiver.
7. Align the recoil pad with the end of the stock and secure it with the two machine screws.

Bolts the pistol grip to the receiver with a new lock-washer, hand tight only, and refits the swivel post (WP 0026 00). The manual puts this in Chapter 3, Unit Maintenance, with the small arms repairman tool kit; the Maintenance Allocation Chart (WP 0034 00) lists Repair of this group at direct support (F).

Applies to: Military pistol grip assembly P/N 7995P (AAL item)

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0026 00, p. 0026 00-2 archive.org [3]

1. Align the pistol grip to the receiver.
2. Place a new lock-washer and the washer on the hex screw and insert it into the pistol grip.
3. Tighten the hex screw hand tight only.
4. Install the swivel post.

Model 500: spring and follower go into the tube, then the tube is screwed into the receiver with a strap wrench. Model 590: a replaced tube is screwed in first, then the follower, spring and magazine catch retainer go in. Direct support maintenance (Chapter 4, WP 0028 00).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0028 00, pp. 0028 00-3 to 0028 00-4 archive.org [3]

1. Model 500: insert the magazine spring and the cartridge follower into the magazine tube.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
2. Wrap a wiping rag around the receiver and clamp it in a bench vise with jaw caps, closing the vise just enough to hold it.
   TipOn the Model 590, do this and the next step only if the magazine tube was replaced.
3. Place a strap-style pipe wrench around the magazine tube and turn it to the right (clockwise) to tighten it.
4. Model 590: insert the cartridge follower, the magazine spring and the magazine catch retainer into the magazine tube.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
5. Assemble the weapon (WP 0014 00) and perform a function check.
   TipWP 0028 00 ends with: after any work, check the shotgun for proper functioning before firing live ammunition.

Reverses the bolt disassembly: firing pin group first, then the extractors, then the bolt lock and its pin. Direct support maintenance (WP 0029 00).

Follows TM 9-1005-338-13&P: Technical Manual, Unit and Direct Support Maintenance (including Repair Parts and Special Tools List) for Mossberg 12-Gauge Shotgun, Model 500 (1005-01-295-1832) and Mossberg 12-Gauge Shotgun, Model 590 (1005-01-251-8578) — Headquarters, Department of the Army, p. WP 0029 00, p. 0029 00-2 archive.org [3]

1. Install the firing pin spring, the flat washer, the firing pin and the firing pin retaining pin in the bolt.
2. Install the two cartridge extractor springs, the right-hand and left-hand cartridge extractors, and the two cartridge extractor pins in the bolt.
   WarningTo avoid injury to your eyes, use care when removing and installing spring-loaded parts.
3. Install the bolt lock and the grooved headless pin in the bolt.

The manual's order, which is not simply the reverse of disassembly: forearm and action slide bars go in first, then the elevator, then the bolt in through the barrel opening.

1. Confirm the safety button on the top rear of the receiver is fully rearward in the ON position, and place the receiver with the trigger housing opening upward on a clean surface.
2. Slide the forearm assembly onto the magazine tube, guiding the action slide bars into the corresponding cuts in the front of the receiver.
   WarningBoth action slide bars must enter their cuts. One out of its track will bind the action.
3. Squeeze the elevator arms together enough to position them in the receiver so the studs on the elevator fit into the corresponding 1/4 in (6.4 mm) holes, then pivot the elevator so its forward portion is even with the outside edge of the receiver cavity.
   TipOnly needed if the elevator was removed.
4. Insert the rear of the bolt assembly into the barrel opening of the receiver, with its bolt lock downward toward the front inside top of the receiver, and depress the ejector on the side of the receiver opposite the ejection port so the bolt can slide fully rearward.
   WarningThe ejector must fit into the corresponding slot in the bolt.
5. Position the action slide bars so the notch on the bar is even with the cuts on the inside receiver walls, push the elevator down until it rests against the bolt, and position the rear of the bolt assembly even with the rear of the clearance cuts.
6. With the bolt slide slotted side up and its notch to the rear, assemble the bolt slide by lowering its front first, so its protrusion fits the cut on the bottom of the bolt lock and its two side protrusions fit into each action slide bar slot.
7. Position the cartridge stop and cartridge interrupter in their places on the inside walls of the receiver, with the hooks facing inward toward the centre of the cavity and away from the receiver walls.
8. Cock the hammer, then set the trigger housing assembly into the receiver and insert its retainer pin.
   WarningThe hammer must be fully cocked or the trigger housing will not go into the receiver. Do not force it.
9. Set the barrel into the receiver with a gentle rotational movement, seating the barrel extension fully with the barrel ring over the magazine tube.
10. Install and tighten the takedown screw (500 series) or magazine cap (590 and 835) firmly by hand.
    WarningA loose barrel retainer lets the barrel move under recoil. Check it before every use.
11. Perform the function check.

These are reproduced from government technical manuals, which are not subject to copyright. Manufacturer manual diagrams are not reproduced here — the entry links to the manual instead.