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Lee-Enfield No. 4 Mk I

• moderate
• Shop tier 2
• medium confidence
• Rifle
• surplus
• bolt action
• milsurp
• corrosive ammo
• historic
• rear locking

field strip ~3 min · reassembly ~4 min · detail strip ~40 min

Specifications

Model-specific safety

• Headspace on a Lee-Enfield is set by the bolt head, which comes in numbered sizes. Surplus rifles have often been rebuilt with mixed parts, and a rifle with the wrong bolt head can have dangerous headspace. Have any rifle of unknown history gauged by a gunsmith before firing it.
• The bolt head and bolt body are a matched relationship. Do not swap bolts or bolt heads between rifles.
• The rifle has a rear locking lug arrangement, which means the action flexes more than a front-locking design. That is by design, but it makes headspace checking more important, not less.
• Surplus .303 ammunition is often corrosively primed. Clean with a water-based solvent the same day you shoot.
• Although the magazine is detachable, it was intended to stay with the rifle and be charger-loaded. Verify the chamber independently of the magazine.

Under spring tension

• Mainspring inside the bolt (detail strip)
• Magazine spring

Easily lost parts

Bolt head · Bolt head release catch · Magazine catch · Firing pin

Tools

No tools required for the field strip.

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. A bolt action with straightforward furniture (one-piece fore-end, two bands, guard screws, a stock bolt through the butt). The bolt needs a notched striker tool and has a jumpy V extractor spring, and the bolt head is fitted to the rifle. There are more traps than a modern bolt gun but no timing.

Parts: 57 numbered parts (complete No. 4 Mk I* rifle per the Gun Digest exploded drawing legend 'No. 4, Mark I* (SMLE) Bolt Action Rifle': keys 1-48 plus the 10 'Parts Not Shown' lines, less 'Stripper Clips' (accessory). Magaz), from The Gun Digest Book of Exploded Gun Drawings (975 isometric views) - 'No. 4, Mark I* (SMLE) Bolt Action Rifle' — Gun Digest Books / Krause Publications (scan on archive.org), p. book p. 535 (PDF page 536) archive.org [5].

Bench time: about 35 min to strip, 50 min to rebuild (estimate). Estimate: bolt (bolt head, striker with tool, extractor and V-spring), bolt head release/catch, magazine and catch, trigger guard and trigger, safety, fore-end, bands, handguards, buttstock (stock bolt), sights. Rebuild longer for the striker tension and the band/guard screw sequence.

Small parts: 4 pins, 7 springs, 1 detents or plungers (counted by name in the same legend. Pins: 11 sear pin, 13 trigger pin, 22 magazine catch pin, rear sight base pin (not shown) (25 firing pin not counted). Springs: 7 safety bolt spring, 10 sear spring)

What comes off for coating

• Bolt: bolt head, striker screw, striker, mainspring, cocking piece (with tool), extractor, extractor spring and screw — Lee-Enfield striker tool
• Receiver: bolt head release/catch and spring (Mk I), safety catch and spring, magazine catch, trigger (with trigger guard), rear sight — drift punch
• Stock and furniture: front and rear guard screws, trigger guard, fore-end, front and middle bands and swivels, handguards, buttstock (stock bolt and washer), butt plate and trap — long screwdriver for the stock bolt

Special tools

• Lee-Enfield striker (firing pin) tool — Unscrewing the striker from the cocking piece
• Fine drift punch (<0.04 in) — Easing out the extractor spring
• Long-bladed screwdriver — The stock bolt through the butt trap

Known pain points

• Stripping the bolt: the bolt head is unscrewed, the cocking piece turned down to relieve the mainspring, the striker screw removed, and the striker unscrewed with a takedown tool that engages notches near its tip. (both)
  Source: Exploded View: Lee-Enfield No. 4 Mk I — American Rifleman (NRA) americanrifleman.org [3] — “To remove the striker, insert a takedown tool from the front until the projections on either side of its point engage the notches.”
• The striker has to be unscrewed from the cocking piece with a notched takedown tool while holding the mainspring; the pamphlet warns a makeshift rig can damage it. (both)
  Source: Lee-Enfield Rifle Manual, No.1 Mk III, No.3, No.4, No.5 (Pamphlet 1) — unknown publisher (archive.org "Lots of gun PDFs") archive.org [4] — “may cause damage and should be left to a qualified gunsmith.”
• The V-shaped extractor spring is eased out through a tiny hole in the bolt head with a fine punch and jumps if not covered; it seats on a small projection going back. (both)
  Source: Lee-Enfield Rifle Manual, No.1 Mk III, No.3, No.4, No.5 (Pamphlet 1) — unknown publisher (archive.org "Lots of gun PDFs") archive.org [4] — “To reassemble, place the spring into the extractor slot and seat the small projection on the spring into its seat in the bolt head.”
• The buttstock comes off by a long stock bolt reached through the butt trap. (both)
  Source: Exploded View: Lee-Enfield No. 4 Mk I — American Rifleman (NRA) americanrifleman.org [3] — “insert a long-bladed screwdriver into the recess in the buttstockﾕs rear and turn out the stock bolt (48) and its washer (49).”

Fit or check on rebuild

• Bolt and bolt head fitted to the rifle — Bolts and bolt heads are fitted to their own boltway (headspace); keep the serial-matched bolt with the rifle
  Source: Lee-Enfield Rifle Manual, No.1 Mk III, No.3, No.4, No.5 (Pamphlet 1) — unknown publisher (archive.org "Lots of gun PDFs") archive.org [4] — “They have been fitted to their respective boltways.”
• Fore-end/king screw and band tension — Fore-end bedding pressure and band screw tension affect zero; re-zero after the woodwork is off

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

Procedures

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.

Function check

• Verify the rifle is unloaded before each step.
• Cycle the bolt and confirm it cocks on closing and locks up fully.
• With the action cocked, apply the safety catch and press the trigger. The striker must not release.
• Confirm the safety catch also locks the bolt handle down when applied.
• Release the safety and press the trigger. The striker should release with a firm snap.
• Confirm the two-stage trigger has a distinct first stage and a clean second stage.
• Load dummy rounds into the magazine and confirm they feed without rim lock and eject cleanly.
• If you have any doubt about the rifle's history, have headspace gauged before firing live ammunition.

Maintenance

Lubrication points

• Bolt body and receiver track
• Rear locking lug surfaces
• Cocking cam
• Extractor
• Bolt head threads (a light film)

Cleaning notes

Corrosive primers leave salts that will rust a bore within a day or two. After shooting surplus .303, flush the bore and bolt face with hot soapy water or a water-based solvent, dry completely, then oil. Many No. 4 rifles have two-groove or five-groove barrels — both are correct and neither indicates a worn bore.

Suggested inspection interval: roughly every 300 rounds. This is a general guideline, not a manufacturer specification.

Wear parts to inspect

Bolt head (the numbered size determines headspace) · Extractor and extractor spring · Locking lugs · Magazine feed lips · Firing pin protrusion

Common issues

Also covers

The procedures above are reported to apply to: Rifle No. 4 Mk I* · Rifle No. 4 Mk 2 · Lee-Enfield No. 5 'Jungle Carbine' (with differences). Verify against the manual for your specific model.

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Sourcing