Heckler & Koch MP5

moderate
Shop tier 2
high confidence
Submachine Gun
roller delayed
fluted chamber
push pin receiver
historic
regulated

field strip ~3 min · reassembly ~5 min · detail strip ~35 min

Before you begin Verify this firearm is unloaded. Remove the magazine or empty the cylinder or tube, lock the action open, and check the chamber both by sight and by touch. Keep the muzzle in a safe direction and remove all live ammunition from your work area.

Heckler & Koch limits owner disassembly The maker's own procedure goes as far as: Disassembly into assembly groups (back plate, trigger group, bolt group and recoil spring, handguard), bolt group disassembly and magazine disassembly, as in the SP5 manual.. HK tells SP5 owners to disassemble the pistol only to the extent described in the manual, warning that improper assembly can compromise safety and function. (Heckler & Koch SP5 Series Operator's Manual — same roller-delayed action, semi-automatic — Heckler & Koch, p. 27 hk-usa.com [2])

Specifications

Manufacturer: Heckler & Koch
Origin: Germany
Category: Submachine Gun
Action: Roller-delayed blowback
Calibers: 9x19mm Parabellum
Capacity: 15 or 30 rounds depending on magazine
Production: 1966–present (in-production)
Also known as: MP5A2, MP5A3, SP5 (semi-automatic variant), MP5 pattern clones

Model-specific safety

Never ride the cocking handle forward. Pull it fully to the rear and let it slam home — 'HK slap'. Easing the bolt forward can leave the weapon out of battery.
The cocking handle does not reciprocate with the bolt during firing, but it does lock into a notch. Make sure it is released from the notch before attempting to close the action.
The recoil spring assembly is under compression when the stock is removed.
HK's warning for this action: improper assembly can compromise safety and functioning. Disassemble only to the extent the manual describes.
The locking piece goes into the bolt carrier with its SMOOTH side toward the bottom of the bolt. Assembled the other way up the bolt will not lock correctly.
Cock the hammer before trying to fit the trigger group. An uncocked hammer is the usual reason it will not rotate up into the receiver.

If it will not go back together

Common ways this firearm resists reassembly, and what is actually wrong. Forcing a part that will not seat is how firearms get damaged.

The trigger group will not rotate up into the receiver.

Why The hammer is not cocked.

Fix Cock the hammer on the trigger group, then offer it up and rotate it into the receiver.

Forcing it Forcing it against a forward hammer bends the trigger group housing and the selector shaft.
The bolt head will not snap onto the locking piece.

Why The locking piece is not pressed fully into the carrier and turned to its assembly position, or the bolt head is not offered up with the extractor upwards.

Fix Press the locking piece fully in and hold it, turn it a quarter turn counter-clockwise, then fit the bolt head extractor-up and turn it a quarter turn counter-clockwise until it audibly snaps.
The gun goes together but does not lock up properly, or headspace feels wrong.

Why The locking piece has been fitted upside down.

Fix Strip the bolt group and refit the locking piece with its smooth side toward the bottom of the bolt.

Forcing it HK warns that improper assembly of this action compromises safety and functioning. Do not fire it to find out.

Gunsmith Do not attempt this one yourself.
The handguard will not come off, or will not go back on.

Why It is being pulled straight off or pushed straight on.

Fix To remove, pull it towards the muzzle and then downwards. To fit, place it on the receiver from below and press it rearwards before inserting its pin.

Under spring tension

Recoil spring assembly
Magazine spring
Hammer spring in the trigger group

Easily lost parts

Push pins · Rollers · Locking piece · Firing pin and its spring

Tools

Tool	Required	Used for	Substitute
Punch or the tip of a cartridge	Optional	Pushing out the stock and trigger group push pins if they are tight.

Shop difficulty

Shop tier 2 Tier 2 — moderate among rifles and carbines, for the full job: strip to the parts that get coated and put it back together working. This is the G3 family in 9 mm, and the HK SP5 list has 49 numbered parts with the trigger housing as one assembly. The strip has the same traps: loose rear-sight springs, plungers and balls, the cocking-support clamping sleeve, the trigger housing spring legs, and a locking piece matched to its carrier. Bolt gap has to be measured afterwards.

Parts: 45 numbered parts (complete semi-automatic SP5 (the civilian MP5-pattern pistol/carbine with the same roller-delayed action) per the HK 'SP5 Parts List & Exploded View': keys 1-39 plus the 3 not-pictured items (locking ), from Heckler & Koch SP5 Series Operator's Manual — same roller-delayed action, semi-automatic — Heckler & Koch, p. 51 hk-usa.com [2].

Bench time: about 55 min to strip, 80 min to rebuild (estimate). Estimate: like the G3 strip, scaled to 9 mm: trigger housing, cocking support, rear sight drum, front sight, mag catch, handguard, stock/end cap, bolt group. Rebuild longer for the trigger housing springs, rear sight detents, handguard fit and the bolt-gap check.

Small parts: 6 pins, 5 springs, 1 detents or plungers (counted by name in the same list (line items). Pins: clamping sleeves (roll pins) 4, 9, 14, 28, 30 (30 is 2x) and catch pin 29 = 6 line items / 7 pieces; the two 'locking bolt' push-pins (grip/cap, ha)

What comes off for coating

Trigger housing / grip: hammer and spring, trigger, sear and springs, ejector and spring, safety levers, pistol grip — roll-pin punches
Receiver: magazine catch, pressure spring, pressure piece, push button, clamping sleeves, charging handle, support, detent pin and spring, clamping sleeve, cap/end cap and locking bolt, rear sight drum, springs, plungers, ball and base, front sight, handguard and locking bolt — HK rear sight tool
Bolt group: bolt head, extractor and spring, rollers and holder, clamping sleeves, locking piece, firing pin and spring, recoil spring guide rod assembly

Special tools

HK rear sight adjustment tool — Rear sight drum
Roll-pin punches — Clamping sleeves
Feeler gauges — Bolt gap
Extractor spring tool / small pick — Extractor spring loop

Known pain points

The rear sight drum sits on loose springs and plungers, and the sight base on a ball and spring; they are not captive and fly when the drum comes off. (both)
Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [4] — “WATCH THE SPRINGS AND PLUNGERS UNDER THE TOOL, THEY ARE NOT CAPTIVE”
The cocking handle support is held by a clamping sleeve (roll pin) that only lines up with both holes in one handle position. (both)
Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [4] — “When the clamping sleeve is centered in the top access hole it is not in alignment in the bottom hole.”
In the trigger housing, spring legs have to be positioned correctly as the sleeve and spring go back. (reassembly)
Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [4] — “Replace sleeve in spring and reinstall in rear of housing being careful of the position of the spring legs.”
The locking piece and bolt carrier work as a matched pair; mixing them changes function. (reassembly)
Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [4] — “Do not interchange these locking pieces!!”

See also 4 documented reassembly problems and their fixes.

Fit or check on rebuild

Bolt gap — Measured with feeler gauges after reassembly; out of range means roller/locking piece work
Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [4] — “The distance between the rear of the bolt head and the front of the bolt carrier when the bolt is”
Rear sight zero — The drum and base come off and the rifle must be re-zeroed
Trigger function — Pressure fork and hammer spring seating checked with a function check

This is Pew-Takedown's rating, not the manufacturer's. How tiers are rated. Forum reports are owners' experience, not specifications.

Procedures

Clear and Make Safe

Clear & Make Safe

Point the muzzle in a safe direction and keep your finger off the trigger.
Place the selector on SAFE.
Press the magazine release and remove the magazine.
Removed at this step: Magazine
Pull the cocking handle fully to the rear and lock it into its forward notch to hold the bolt open.
Inspect the chamber and magazine well with a light and physically confirm the chamber is empty.
Release the cocking handle from its notch and let the bolt go forward under spring pressure.
WarningDo not ride it forward. Let it slam.
Remove all live ammunition from the work area.

Field Strip

Complete the Clear and Make Safe procedure with the selector on SAFE, the magazine out and the bolt released forward.
Push in the locking pin or pins for the back plate and pull them out.
TipThe full-size gun has one back plate pin; the K variant has two. The pins can be pushed in from either side of the receiver.
Removed at this step: Back plate locking pins
Remove the back plate or buttstock to the rear.
Removed at this step: Back plate / buttstock
Remove the pistol grip and trigger group downwards.
Removed at this step: Trigger group
Pull the bolt group and recoil spring rearwards out of the receiver.
Removed at this step: Bolt group Recoil spring
Push in the locking pin for the handguard and pull it out.
Pull the handguard towards the muzzle, then downwards, to remove it.
TipForward first, then down. It does not come straight off.
Removed at this step: Handguard

Bolt Group Disassembly

Detail Strip

Routine for cleaning. The rollers and locking piece are what make this action work — handle them carefully.

Strip the firearm into assembly groups first.
Turn the bolt head and locking piece clockwise.
Remove the bolt head and locking piece from the bolt carrier by bringing them forward.
Removed at this step: Bolt head Locking piece
Remove the firing pin and its pressure spring forward out of the bolt carrier.
Removed at this step: Firing pin Firing pin pressure spring
Clean the bolt head, its roller recesses, the locking piece and the carrier interior.
WarningHK's published strip stops here. Driving the rollers out of the bolt head is armorer work and is not part of routine cleaning.
To reassemble: push the pressure spring onto the firing pin and place both into the locking piece.
Press the locking piece completely into the bolt carrier and hold it there.
WarningThe smooth side of the locking piece faces the bottom of the bolt. Check this before going further.
Turn the locking piece counter-clockwise a quarter turn until it reaches its assembly position.
Place the bolt head onto the locking piece with the extractor upwards.
Turn the bolt head counter-clockwise a quarter turn until the connecting piece audibly and tangibly snaps into place.
WarningYou should hear and feel it. If it does not snap, it is not assembled.

Reassembly

Assemble the bolt group.
Place the handguard onto the receiver from below and press it rearwards.
Push the handguard locking pin into the receiver.
TipLocking pins can be pushed in from either side.
Insert the bolt group and recoil spring into the receiver from the rear.
Cock the hammer, then insert the trigger group into the receiver and rotate it upwards.
WarningCock the hammer first. This is the step people miss when the trigger group will not go in.
Insert the back plate or buttstock into the receiver.
Push the back plate locking pin or pins into the receiver.
Pull the cocking handle fully back and release it sharply, then perform the function check.

Torque specifications

No sourced torque values from the manufacturer are recorded for this firearm. Where a fastener has a specified torque — action screws, scope bases, muzzle devices, barrel nuts — get it from the manufacturer or a gunsmith rather than estimating it.

What the manufacturer does say: The manufacturer's documents give no torque value. They say: "Tighten the set screw by turning clockwise with Phillips-head screwdriver." (Heckler & Koch SP5 Series Operator's Manual — same roller-delayed action, semi-automatic, PDF p. 21 (rear sight windage adjustment)) "Only remove the Picatinny rail scope mount if it is damaged." (Operator's Manual SP5 Series (5.12.2026 FINAL), PDF p. 25)

Function check

After every reassemblyPerform these checks on a verified-unloaded firearm. If any check fails, the firearm is not safe to fire — stop and see a licensed gunsmith.

Verify the weapon is unloaded with no magazine inserted before each step.
Pull the cocking handle fully rearward and release it sharply. The bolt should go fully into battery.
With the selector on SAFE, press the trigger. The hammer must not fall.
Move the selector to semi-automatic, cock the action, and press the trigger. The hammer should fall.
Hold the trigger back, cock the action, and release the trigger to feel the disconnector reset.
Confirm the cocking handle locks into and releases from its notch cleanly.
Confirm both push pins are fully seated and the stock and trigger group are secure.
If the bolt does not go fully into battery, do not fire. Have the bolt gap checked.

Maintenance

Lubrication points

Bolt carrier exterior
Locking piece ramps
Rollers and their recesses
Receiver interior where the carrier rides
Hammer and sear pivots

Cleaning notes

The fluted chamber is a design feature, not fouling — do not attempt to polish the flutes out. Clean them, but leave them alone otherwise. Keep the roller recesses and locking piece ramps clean and lightly lubricated; that interface is what controls the delay.

Suggested inspection interval: roughly every 1000 rounds. This is a general guideline, not a manufacturer specification.

Wear parts to inspect

Rollers (inspect for flats and chipping) · Locking piece · Bolt head · Extractor and extractor spring · Recoil spring

Common issues

Symptom	Likely cause	What to do
Bolt does not go fully into battery	Riding the cocking handle forward, or a worn locking piece and out-of-spec bolt gap	Always release the cocking handle sharply. If it persists, have the bolt gap measured against specification. see a gunsmith
Brass showing heavy longitudinal scoring	Normal — the fluted chamber marks cases by design	This is expected on a roller-delayed action and is not a fault.
Failures to extract on a clone build	Out-of-spec bolt gap, extractor, or chamber	Have the bolt gap measured and the extractor inspected before troubleshooting further. see a gunsmith

Also covers

The procedures above are reported to apply to: MP5A2, A3, A4, A5 · MP5K and MP5SD (with significant differences) · H&K SP5 · MP5-pattern semi-automatic clones. Verify against the manual for your specific model.

Similar manual of arms

Heckler & Koch VP9

Legal notes

Not legal adviceSelect-fire MP5s are heavily regulated in most jurisdictions, including as machine guns under U.S. federal law. Semi-automatic variants and clones are regulated differently, and configurations combining a short barrel with a stock may themselves be regulated. This entry documents maintenance only. Know the law that applies to your specific weapon and configuration.

Sourcing

Confidence: high — Cross-checked against a primary source such as the manufacturer's manual or an issuing military technical manual.
Verification: Checked against an armorer/technical manual
Last updated: 2026-10-29

References

Every source this page draws on, with its web address so you can read it yourself. Numbers in brackets elsewhere on the page point here.

[1] Heckler & Koch MP5 Submachine Gun Operator's and Armorer's Manual — Heckler & Koch GmbH armorer course primary source
[2] Heckler & Koch SP5 Series Operator's Manual — same roller-delayed action, semi-automatic — Heckler & Koch manufacturer manual primary source
https://hk-usa.com/wp-content/uploads/2026/09/SP5-Series-Operators-Manual-9.11.26-FINAL.pdf (checked 2026-09-15)
[3] Operator's Manual SP5 Series (5.12.2026 FINAL) — Heckler & Koch USA (Heckler & Koch, Inc.) manufacturer manual primary source
https://hk-usa.com/wp-content/uploads/2026/05/SP5-Series-Operators-Manual-5.12.2026-FINAL.pdf (checked 2026-09-27)
[4] MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division manufacturer manual primary source
https://archive.org/download/MManuals/HkMp5ArmorersManual.pdf (checked 2026-10-29)

Notes: Disassembly and reassembly checked on 2026-09-15 against HK's SP5 Series operator's manual (56 pages), section 6, and corrected where they differed. Be clear what that source is: the SP5 is HK's semi-automatic 9 mm pistol on the same roller-delayed action, with the same assembly groups and bolt group. It is NOT the select-fire MP5's own manual, which is why verification stays armorer-manual-verified. The MP5 differs in trigger group and fire selector; the field strip and bolt group are common to both. HK also publishes an MP5 .22 LR manual for the Umarex rimfire lookalike — a simple blowback with none of this mechanism. It was deliberately not used as a source. Details newly taken from HK: the locking piece is fitted smooth side toward the bottom of the bolt; the bolt head goes on extractor-upwards and turns a quarter turn counter-clockwise until it audibly snaps; the hammer must be cocked before the trigger group will rotate in; the handguard comes off forward then down. Driving the rollers out of the bolt head is not in HK's published strip and is marked armorer work. K, SD and PDW variants differ in handguard, stock and barrel assembly, and clone fitment varies. Bolt gap is not published here — measuring and correcting it needs gauges and fitted parts.

Found something wrong? Corrections are the most valuable contribution to this project. Open an issue with the model, the step, and a source.