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Work order — Mossberg 590A1

Taking the firearm apart for a job such as refinishing, and putting it back together to specification. Generated from the Pew-Takedown entry last updated 2026-10-29. Confidence: high.

Shop difficulty: Tier 1 of 3

Same 500-family action: about 51 listed items (groups listed as assemblies), slip-fit parts and one push pin; traps are the bolt-slide/action-bar alignment, the hammer-cocked/safety-on order and the 590's heavily loaded magazine spring retainer. Heavier barrel and metal trigger guard do not add steps. 51 parts (Generic parts list for the 500/505/510/535/590/835 pump family (names the 590 only in row 34, magazine cap); not 590A1-specific; trigger housing and bolt listed as assemblies). Pew-Takedown's rating, not the manufacturer's.

Bench time: strip ~35 min, rebuild ~50 min (estimate). Actual: strip ______ rebuild ______

Special tools:

• Tube nut tool — Forend action slide tube nut
• Strap wrench and padded vise — Magazine tube off the receiver
• Long socket extension — Stock bolt deep in the buttstock
• Roll/pin punches 1/16-1/8 in. — Bolt extractor and firing pin pins

Watch for:

• The bolt, bolt slide and both action slide bars have to go back in the same relationship they came out; a bar out of its cut or a bolt slide offered at the wrong point of forend travel will not drop in or binds the action. (reassembly; O.F. Mossberg & Sons, Inc.)
• On 590-pattern guns the magazine spring retainer and spring are under significant pressure when the cap comes off or goes back on. (both; O.F. Mossberg & Sons, Inc.)
• Owners report the shell stop and interrupter get jammed in wrong and the action bars mis-seated when the gun is forced together; it only runs once everything lines up. (reassembly; Calguns.net)
• The hammer must be at full cock to get the trigger housing back in, and the safety must be on to reinstall the bolt; neither is obvious and forcing it damages parts. (reassembly; American Rifleman (NRA))
• The action slide tube nut that holds the forend on is removed and refitted with a dedicated tube nut tool. (both; Headquarters, Department of the Army)

Tools

• Punch (roughly 1/8 in) — Pushing out the trigger housing pin if tight.

1. Clear and make safe

Manufacturer's video: Loading and Unloading - Mossberg 500 / 590 Series Shotguns (MOSSBERG)
https://www.youtube.com/watch?v=3_ufCUSZ27s

1. Point the muzzle in a safe direction and keep your finger off the trigger.
2. Push the tang safety rearward to the safe position.
3. Press the action lock lever on the left side behind the trigger guard and pull the forend rearward to open the action.
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, inspect the chamber and look up the magazine tube with a light.
   Warning: The chamber AND the tube. A shell hung up in the tube is easy to miss.
6. Physically confirm the chamber is empty and remove all live ammunition from the work area.

2. Disassemble

Field Strip

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 until the front of the bolt sits in the middle of the ejection port.
   Warning: Do not skip this. The barrel will not come out cleanly unless the bolt is positioned here first.
4. Unscrew the magazine cap counterclockwise from the muzzle end of the magazine tube.
   Warning: The magazine spring retainer and spring are under significant spring pressure.
5. Remove the barrel from the receiver with a gentle back-and-forth rotational movement while pulling it out.
   Tip: Rotate as you pull. Pulling straight out is the common mistake.
6. Position the shotgun with the trigger guard upward.
7. Using a punch no greater than 3/16 in (4.76 mm) in diameter, push out the trigger housing retainer pin from the side of the receiver, roughly 1/2 in (12.7 mm) below the rear of the trigger guard.
8. Remove the trigger housing assembly by lifting the rear portion upward first.
   Warning: Once it is out, do not pull the trigger and let the hammer fall.

Remove the interrupter, cartridge stop, bolt slide, bolt and elevator

1. With the barrel and trigger mechanism removed, take the cartridge interrupter out of the ejection-port side of the receiver.
   Warning: Do not allow the hammer to fall when removing the trigger group from the receiver. Personal injury or damage to the trigger assembly may result.
2. Remove the cartridge stop from the opposite side of the receiver.
3. Note the position of the bolt, bolt slide and action bar assembly.
   Tip: These parts must be in the same relationship during assembly.
4. Move the forearm and action slide assembly rearward until the bolt and bolt slide are three quarters of the way rearward.
5. When the bottom of the bolt slide lines up with the clearance cuts in the side of the receiver, lift the bolt slide up and out of the receiver.
6. Remove the fore end assembly from the magazine tube.
7. Push the bolt out of the front of the receiver.
8. Compress the elevator and remove it from the receiver.

Disassemble the fore end assembly

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.
   Tip: The tube nut tool is a manufactured item; WP 0030 00, Figure 1 gives its dimensions (1080 bar stock).
3. Remove the slide grip and the anti-rattle spring from the action slide assembly.
   Warning: To avoid injury to your eyes, use care when removing and installing spring-loaded parts.

Strip the barrel assembly (heat shield, front sight, sling swivel)

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.
   Tip: Discard the self-locking nuts; new ones are used on assembly.
3. Remove the front sight from the barrel.
4. On the Model 500, remove the retaining ring and the machine screw from the barrel.
5. Remove the sling swivel only if it is damaged. On an old-style swivel, remove the screw, the swivel and the sleeve bushing.
6. On a new-style swivel, turn the locking knob fully counterclockwise.
   Tip: Removal 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.
8. Turn the swivel post counterclockwise to remove it.

Remove the buttstock and recoil pad

1. Remove the two machine screws and the recoil pad from the stock.
2. Remove the machine screw, washer and lock-washer from inside the stock.
   Tip: Discard the lock-washer; a new one (P/N 7615P) is used on assembly.
3. Separate the stock from the receiver.
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.
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.
6. Turn the swivel post counterclockwise to remove it.

Remove the pistol grip assembly

1. Field strip the shotgun (WP 0014 00).
2. Remove the hex screw, washer and lock-washer from the pistol grip.
   Tip: Discard the lock-washer; a new one (P/N 7613P) is used on assembly.
3. Remove the swivel post.

Remove the magazine spring, follower and magazine tube

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.
   Warning: To avoid injury to your eyes, use care when removing and installing spring-loaded parts.
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.
   Tip: On 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.
6. Model 500: remove the cartridge follower and the magazine spring from the magazine tube.
   Warning: To avoid injury to your eyes, use care when removing and installing spring-loaded parts.

Disassemble the bolt assembly

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.
3. Remove the two cartridge extractor pins, the left-hand and right-hand cartridge extractors, and the two extractor springs from the bolt.
   Warning: To avoid injury to your eyes, use care when removing and installing spring-loaded parts.
4. Remove the firing pin retaining pin, the firing pin, the flat washer and the spring from the bolt.
   Tip: WP 0029 00 calls this spring the 'follower spring'; the parts list (WP 0040 00, item 9) names it SPRING, FIRING PIN.

3. Refinish

The components the procedures above separate. Coating, masking and cure are outside this database; follow your coating system's instructions. A part the manufacturer marks "factory fit" should not be swapped or reworked.

No manufacturer statement of materials or finish is recorded. Identify each part's material before choosing prep and cure.

The manufacturer's full parts list (51 parts) is on the reference page.

4. Reassemble

Disassemble the bolt assembly

1. Reverse the steps of "Disassemble the bolt assembly".

Remove the magazine spring, follower and magazine tube

1. Reverse the steps of "Remove the magazine spring, follower and magazine tube".

Remove the pistol grip assembly

1. Reverse the steps of "Remove the pistol grip assembly".

Remove the buttstock and recoil pad

1. Reverse the steps of "Remove the buttstock and recoil pad".

Strip the barrel assembly (heat shield, front sight, sling swivel)

1. Reverse the steps of "Strip the barrel assembly (heat shield, front sight, sling swivel)".

Disassemble the fore end assembly

1. Reverse the steps of "Disassemble the fore end assembly".

Remove the interrupter, cartridge stop, bolt slide, bolt and elevator

1. Reverse the steps of "Remove the interrupter, cartridge stop, bolt slide, bolt and elevator".

Install the elevator, bolt, bolt slide, interrupter and cartridge stop

1. Make sure the safety is on SAFE (fully to the rear).
2. Insert the compressed elevator into the receiver.
3. Depress the ejector and insert the bolt into the receiver.
4. Push the sides of the elevator down beside the bolt and slide the bolt back.
5. Install the fore end assembly over the magazine tube, inserting the action bars into the slots in the front of the receiver on either side of the magazine tube.
   Tip: Having the fore end about three quarters of the way forward eases installation of the bolt slide.
6. Insert the bolt slide, lowering the front end and inserting the rear end first so its lug fits the slot in the bolt lock and is retained by the action bar.
7. Push the bolt slide down and move the action slide to the rear until it engages.
8. Move the bolt, bolt slide and action forward.
9. Insert the cartridge interrupter and the cartridge stop.
10. Make sure the hammer is fully cocked.
    Tip: The hammer must be fully cocked for the trigger housing to go into the receiver.
11. Hold the cartridge stop and cartridge interrupter firmly against the receiver walls with one hand and grasp the trigger mechanism with the other.
12. Insert the lugs on each side of the front cover of the trigger mechanism into the slots on each side of the receiver.
13. Ease the rear of the trigger mechanism down into position without forcing it.
    Tip: If it does not fit easily, check that all internal pins in the trigger mechanism are flush with the side of the housing and that the cartridge stop and interrupter are positioned correctly.
14. Align the pin holes and insert the trigger housing retainer pin until it is flush on both sides.

Reassemble the fore end assembly

1. Slide the slide grip onto the action slide assembly.
   Warning: To 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.

Reassemble the barrel assembly

1. Install the swivel post by turning it clockwise.
   Tip: If 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.

Install the buttstock and recoil pad

1. Install the swivel post by turning it clockwise.
   Tip: If 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.

Install the pistol grip assembly

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.

Install the magazine tube, spring and follower

1. Model 500: insert the magazine spring and the cartridge follower into the magazine tube.
   Warning: To 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.
   Tip: On 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.
   Warning: To 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.
   Tip: WP 0028 00 ends with: after any work, check the shotgun for proper functioning before firing live ammunition.

Reassemble the bolt assembly

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.
   Warning: To 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.

Reassembly

1. Confirm the safety is fully rearward in the ON position and place the receiver with the trigger housing opening upward.
2. Slide the forearm assembly onto the magazine tube, guiding both action slide bars into the corresponding cuts in the front of the receiver.
   Warning: Both bars must enter their cuts. One out of its track will bind the action.
3. Insert the rear of the bolt assembly into the barrel opening with its bolt lock downward, depressing the ejector so the bolt can slide fully rearward.
   Warning: The ejector must fit into the corresponding slot in the bolt.
4. Fit the bolt slide, slotted side up and notch to the rear, lowering its front first so its protrusions engage the bolt lock cut and both action slide bar slots.
5. Cock the hammer, then set the trigger housing assembly into the receiver and insert its retainer pin.
   Warning: The hammer must be fully cocked or the trigger housing will not seat. Do not force it.
6. Set the barrel into the receiver with a gentle rotational movement, seating the extension fully with the barrel ring over the magazine tube.
7. Install and hand-tighten the magazine cap firmly.
   Warning: A loose barrel retainer lets the barrel move under recoil. Check it before every use.
8. Perform the function check.

5. Torque

No manufacturer torque values are recorded for this firearm.

Reported by other sources — not the manufacturer

Notes: The manufacturer's documents give no torque value. They say: "Using hex wrench supplied, tighten bolt snugly." (Owner's Manual for 500, 505, 510, 535, 590 and 835 Pump Action Shotguns, PDF p. 21) "tighten the clamp screws to securely hold the heat shield in place. DO NOT OVERTIGHTEN THE SCREWS." (Owner's Manual for 500, 505, 510, 535, 590 and 835 Pump Action Shotguns, PDF p. 28)

Fit or check on rebuild

• Magazine tube torqued and aligned to the barrel lug — Tube carries the barrel; it is refitted hand-tight-plus with a strap wrench and must line up with the takedown screw or cap.
• Safety detent feel — The tang safety's ball and spring under the detent plate set the click; a missing ball gives a loose safety.
• Function check: safety, trigger/sear release, disconnector and feeding with dummy rounds — Standard after any detail strip; a mis-assembled sear or disconnector can double or fail to fire.

6. Function check

• After any cleaning or disassembly, check the shotgun for proper functioning before firing live ammunition.
• Move the safety fully rearward to ON and keep the muzzle in a safe direction.
• Open the action and visually and physically check the chamber, elevator, and magazine tube.
• Depress and hold the action lock lever, then open and close the action several times to check for free movement.
• Close the action, leave the safety ON, and pull the trigger fully rearward. The hammer should not fall.
• Remove your finger from the trigger and move the safety to OFF. The hammer should not fall.
• With the safety OFF, pull the trigger. The hammer should fall.
• Load two dummy shells and confirm they feed and eject one per cycle.
• Confirm the magazine cap is tight.

If any check fails, the firearm is not safe to fire. Stop and see a licensed gunsmith.

Sources

1. Owner's Manual for 500, 505, 510, 535, 590 and 835 Pump Action Shotguns — O.F. Mossberg & Sons, Inc. primary
   https://resources.mossberg.com/hubfs/manuals/12173-Owners-Manual-Pumps-English.pdf
2. Mossberg 590 / Remington 970 Stock - MI-SG-590 / MI-SG-870 installation instructions — Midwest Industries, Inc. secondary
   https://midwestindustriesinc.com/content/installation-instructions/Mossberg-590-Remington-970-Stocks-Instructionrs.pdf
3. 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 primary
   https://archive.org/download/16-manuali-duso-e-manutenzione-per-armi-specifiche-use-and-maintenance-manuals-f_20230430/ARMY%20TM%209-1005-338-13%26P%20Technical%20Manual%20for%20Mossberg%2012-Gauge%20Shotgun%20Model%20500%2C%20590%20-%20May%202005.pdf
4. Magpul MAG493 Forward Sling Mount – Mossberg 590A1 — Installation Instructions — Magpul Industries secondary
   https://magpul.com/media/wysiwyg/Instructions/MAG493_Forward_Sling_Mount_Mossberg_INSRT.pdf
5. Mesa Tactical Telescoping Stock & Adapter Shotgun Conversion Kit — Assembly Guide (#47371 Rev II) — Mesa Tactical secondary
   https://mesatactical.com/content/manuals/47371_Stock_Adapter_Manual_rev_ii.pdf
6. Seeking help from someone who owns a Mossberg 500 in the Bay Area — Calguns.net anecdotal
   https://www.calguns.net/forum/general-discussion/general-gun-discussions/910351-seeking-help-someone-own-mossberg-500-in-bay-area?p=21089362
7. The Mossberg Model 500: History & Disassembly — American Rifleman (NRA) secondary
   https://www.americanrifleman.org/content/the-mossberg-model-500-history-disassembly

Educational guide only. Some information comes from non-authoritative sources. Always consult your manufacturer's manual and a licensed gunsmith. Verify your firearm is unloaded before every procedure. Full disclaimer: https://github.com/Fundamental-build-LLC/Pew-Takedown

Legal notice: this material is third-party information compiled from sources of varying reliability and is provided for general informational and educational purposes only. It is not gunsmithing, technical, safety or legal advice, it is not verified or endorsed by any manufacturer, and it must not be taken as fact. Any work on a firearm beyond the routine field stripping described in its own owner's manual should be performed only by a licensed and insured gunsmith. You use this material entirely at your own risk. Fundamental Build LLC and the project's contributors make no warranty of any kind and accept no liability for death, injury, damage or loss arising from its use. Full terms: LEGAL.md.