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Work order — Benelli M4

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: medium.

Shop difficulty: Tier 2 of 3

More systems than the inertia guns (twin gas pistons and cylinder plugs, rotating bolt with cam pin, link and recoil spring tube in the stock) and the Marine Corps stops operators at field strip, but each step is a single orientation or held-spring trap rather than timing. Top of Tier 2. Pew-Takedown's rating, not the manufacturer's.

Bench time: strip ~60 min, rebuild ~85 min (estimate). Actual: strip ______ rebuild ______

Special tools:

• Bolt handle (used as the issued tool) — Gas cylinder plugs and trigger group pin
• 18-19 mm or 1-1/16 in. wrench on the receiver extension flats — Receiver extension removal (bare-receiver jobs)
• Punch set — Bolt pins

Watch for:

• The Marine Corps manual stops operator disassembly at the field strip; anything past that is armorer work. (both; Headquarters, U.S. Marine Corps (Marine Corps Systems Command))
• The firing pin is pushed in against its spring while the retaining pin is inserted, and the pin must not be pushed fully behind the firing pin. (reassembly; Headquarters, U.S. Marine Corps (Marine Corps Systems Command))
• The two gas pistons have a front and a back; reversed they will not seal, and both must enter their holes in the receiver as the barrel goes on. (reassembly; Headquarters, U.S. Marine Corps (Marine Corps Systems Command))
• When the bolt goes back in, the link has to slide over the trigger guard and onto the recoil spring plunger hidden inside the receiver; if it misses, the gun will not cycle and the plunger can be damaged. (reassembly; Benelli USA / Benelli Armi S.p.A.)
• The magazine cap and spring seal ring are under considerable spring tension when the magazine is stripped. (both; Headquarters, U.S. Marine Corps (Marine Corps Systems Command))

1. Clear and make safe

1. Point the muzzle in a safe direction and keep your finger off the trigger.
2. Engage the crossbolt safety at the trigger guard.
3. Pull the bolt handle rearward to eject any chambered shell and lock the bolt open.
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.
2. Unscrew the magazine cap from the end of the magazine tube and remove the forend.
3. Pull the barrel forward off the magazine tube and out of the receiver.
4. Withdraw the two gas pistons from their cylinders in the barrel assembly, noting their orientation.
   Warning: Note which way each piston faces before it comes out.
5. Pull the bolt handle out of the bolt.
6. Slide the bolt assembly forward and out of the receiver.
7. Push out the trigger group pin and lift the trigger group out of the receiver.

Remove the magazine spring seal ring, spring and follower

1. Place the bolt group in the forward position.
2. Remove accessories such as the sling, targeting devices and lights.
3. Unscrew the magazine cap counterclockwise as viewed from the front of the weapon.
   Warning: Make sure the muzzle end of the magazine points in a safe direction while removing the magazine cap and the magazine spring seal ring. The magazine parts are under considerable spring tension and can injure you or bystanders if released. If the magazine spring seal is worn, it may come out when the cap is removed and eject the magazine spring.
4. Pull the bolt handle out of the bolt group.
5. Use the bolt handle to remove the magazine spring seal ring from the magazine tube.
   Warning: Make sure the muzzle end of the magazine points in a safe direction while removing the magazine cap and the magazine spring seal ring. The magazine parts are under considerable spring tension and can injure you or bystanders if released. If the magazine spring seal is worn, it may come out when the cap is removed and eject the magazine spring.
6. Remove the magazine spring and the follower from the magazine tube.
   Tip: Tap the magazine on a padded surface to get the follower out.

Remove the telescoping buttstock and pistol grip

1. Remove the trigger group from the receiver (field strip).
   Tip: The manual's stock removal starts 'With the trigger guard removed'.
2. With the buttstock collapsed, grip it with your firing hand and depress the button with your thumb.
3. Rotate the telescoping buttstock clockwise and pull it to the rear.
4. When the buttstock is fully extended, rotate it counterclockwise to the vertical position and release the button.
5. Grip the extended buttstock with your firing hand, depress the button, and keep it fully depressed while you rotate the buttstock module clockwise.
   Tip: The manual's note: keep the button completely depressed while removing the buttstock.
6. Push the buttstock module in to the inscribed line on the recoil tube.
7. When the forward edge of the buttstock module reaches the inscribed line, rotate the buttstock counterclockwise until the top of the telescoping module lines up with the flat part of the recoil tube.
8. Pull the telescoping buttstock to the rear off the recoil tube.
9. Unscrew the pistol grip counterclockwise until it is free and remove it to the rear over the recoil tube.

Disassemble the bolt group

1. Remove the bolt group from the receiver (field strip).
   Warning: Do NOT remove the extractor, link or bolt handle retaining pin during operator disassembly. It is not required to remove these parts for operator cleaning or maintenance.
2. Place a finger over the rear end of the firing pin and remove the firing pin retaining pin from the right side of the bolt carrier.
3. Lift the firing pin, with its spring, out of the recess in the rear of the bolt carrier.
4. Separate the firing pin spring from the firing pin.
5. Lift or shake the cam pin out of the bolt assembly.
6. Pull the bolt head out of the bolt carrier.

Remove the gas cylinder plugs and gas pistons

1. Remove the barrel from the receiver (field strip).
   Tip: The gas system need not be taken apart at every field strip; the manual calls for it every 5,000 rounds or when there is water, debris or excessive fouling in the gas system.
2. Using the bolt handle, unscrew the gas cylinder plugs counterclockwise as viewed from the front of the barrel.
3. Remove the gas pistons from the front end of the gas cylinders.

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.

4. Reassemble

Remove the gas cylinder plugs and gas pistons

1. Reverse the steps of "Remove the gas cylinder plugs and gas pistons".

Disassemble the bolt group

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

Remove the telescoping buttstock and pistol grip

1. Reverse the steps of "Remove the telescoping buttstock and pistol grip".

Remove the magazine spring seal ring, spring and follower

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

Install the magazine follower, spring and spring seal ring

1. Insert the magazine follower into the end of the magazine tube with its red, smaller-diameter end with the raised tactile ring going in first.
2. Insert the magazine spring into the magazine tube behind the follower.
3. Insert the magazine spring seal ring, squeezing it and pressing down from the top while rotating it forward until the seal is set.
   Warning: Make sure the muzzle end of the magazine points in a safe direction while removing the magazine cap and the magazine spring seal ring. The magazine parts are under considerable spring tension and can injure you or bystanders if released. If the magazine spring seal is worn, it may come out when the cap is removed and eject the magazine spring.
   Tip: Figure 42 shows the three stages of seating the seal ring.
4. Install the barrel and forearm, then screw the magazine cap on hand tight to the last click.
   Tip: The manual's step 8 holds the bolt group at least 1/4 in to the rear with the bolt handle while the barrel extension goes in, and checks that both gas pistons enter their holes in the front of the receiver.

Install the pistol grip and telescoping buttstock

1. Place the pistol grip over the rear end of the recoil spring tube at the back of the receiver.
2. Screw the pistol grip onto the receiver clockwise, as viewed from the rear, until it is flush against the back of the receiver and vertical.
3. Grip the telescoping buttstock with your firing hand and depress the button.
4. Rotate the buttstock counterclockwise until its top lines up with the flat part of the recoil tube.
5. Push the buttstock up the recoil tube to the inscribed line.
6. Rotate the buttstock clockwise past vertical and push it forward.
7. Rotate the buttstock counterclockwise and release the button.

Reassemble the bolt group

1. Insert the bolt head into the front of the bolt carrier with the extractor to the right.
2. Insert the cam pin through the hole in the bolt head so that the hole through the cam pin and the index line on its top run parallel with the bolt carrier.
3. Place the firing pin spring onto the front end of the firing pin.
4. Insert the firing pin, with its spring, into the hole in the back end of the bolt carrier.
5. Press in on the back of the firing pin with your finger against spring tension and push the firing pin retaining pin into the bolt carrier from right to left.
   Warning: Do not try to place the firing pin retaining pin completely behind the end of the firing pin.
6. Check that the back end of the firing pin is visible at the back of the bolt carrier and that the firing pin moves freely when pushed in with a pointed object.

Install the gas pistons and gas cylinder plugs

1. Install the gas pistons in the gas cylinders with the long extension facing the rear of the barrel.
2. Install the gas cylinder plugs and tighten them clockwise, as viewed from the front of the barrel, using the bolt handle.

Reassembly

1. Install the trigger group into the receiver and insert its pin fully.
2. Slide the bolt assembly into the receiver, engaging the link with the recoil spring plunger.
3. Install the bolt handle into the bolt.
4. Reinstall the two gas pistons into their cylinders in the correct orientation.
   Warning: Reversed pistons will not seal and the shotgun will not cycle correctly.
5. Set the barrel into the receiver with its extension seated fully and its ring over the magazine tube.
6. Install the forend and thread the magazine cap on, hand-tightening firmly.
   Warning: A loose magazine cap causes malfunctions and lets the barrel move. Check it before every use.
7. Cycle the action several times and 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: "Screw on the fore-end fastening cap, on the end of the tubular magazine and tighten firmly until the barrel and the fore grip are locked perfectly against the receiver (fig. 10)." (M4 Tactical Shotgun Product Manual, PDF p. 49)

Fit or check on rebuild

• Gas pistons installed long extension rearward and entering the receiver holes — Reversed or misaligned pistons will not seal and the gun will not cycle.
• Link aligned with the recoil spring tube — Bolt must move freely; a misaligned link binds.
• 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

• Verify the shotgun is unloaded — chamber and magazine tube — before each step.
• Cycle the action by hand and confirm the bolt locks fully into battery.
• With the hammer cocked, engage the safety and press the trigger. The hammer must not fall.
• Disengage the safety and press the trigger. The hammer should fall.
• Confirm the bolt locks open when retracted and releases with the carrier release.
• Load two dummy shells into the magazine and confirm they feed and eject one at a time.
• 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. Benelli M4 Use and Maintenance Manual — Benelli Armi S.p.A. primary
2. TM 10698A-10/1 (preliminary): Operator's Manual, Shotgun, Combat, 12 Gauge, Semi-Automatic, M1014 — U.S. Marine Corps primary
3. M4 Tactical Shotgun Product Manual — Benelli USA / Benelli Armi S.p.A. primary
   https://www.benelliusa.com/sites/default/files/content/media/manuals/2019-10/M4%20Tactical%20Shotgun%20Product%20Manual.pdf
4. Benelli M4 Black — technical data — Benelli Armi S.p.A. primary
   https://www.benelli.it/en/arma/m4-black
5. TM 10698A-10/1 (preliminary): Preliminary TM 10698A-10/1, U.S. Marine Corps Technical Manual: Operator's Manual for Shotgun, Combat, 12 Gauge, Semi-Automatic, M1014 (1005-01-472-3147) [For Official Use Only] — Headquarters, U.S. Marine Corps (Marine Corps Systems Command) primary
   https://archive.org/download/benelli-m-4-usmc-manual/Benelli%20M4%20%28USMC%20Manual%29_text.pdf
6. Midwest Industries Benelli M4 Handguard (MI-BENM4-HG) — Instructions — Midwest Industries, Inc. secondary
   https://midwestindustriesinc.com/content/installation-instructions/Benelli-M4-Handguard-MI-BENM4-HG-Instructions.pdf
7. Mesa Tactical Reflex Sight Mounts Manual (46020 rev e) — Mesa Tactical secondary
   https://mesatactical.com/content/manuals/46020_Reflex_Sight_Mounts_Manual_rev_e.pdf
8. Mesa Tactical SureShell Carrier and ACRO Sight Mount Manual (46028) — Mesa Tactical secondary
   https://mesatactical.com/content/manuals/46028_SureShell_Carrier_and_ACRO_Sight_Mount_Manual.pdf
9. Mesa Tactical SureShell Shotshell Carriers — Assembly and Operation Guide (47374) — Mesa Tactical secondary
   https://mesatactical.com/content/manuals/47374_SureShell_Shotshell_Carriers_Assembly_and_Operation_Guide.pdf

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.