Schmidt-Rubin K31

moderate
Shop tier 1
medium confidence
Rifle
surplus
milsurp
corrosive ammo
historic
straight pull
detachable magazine
service rifle
collectible

field strip ~3 min · reassembly ~4 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.

Specifications

Manufacturer: Waffenfabrik Bern
Origin: Switzerland
Category: Rifle
Action: Bolt action
Calibers: 7.5x55mm Swiss (GP11)
Capacity: 6 rounds in the detachable magazine, charger loaded
Production: 1933–1958 (surplus)
Also known as: Karabiner Modell 1931, K31

Model-specific safety

Trigger press: not confirmed either way This entry records that no trigger press is needed to disassemble, but that has not been checked against the manufacturer's manual — no manual is cited here yet. Several entries in this database were found asserting exactly this and turning out to be wrong. Treat the takedown as if a trigger press may be required: confirm the chamber is empty before you begin, and check your own manual.

These rifles are decades old and most have been arsenal rebuilt with mixed parts. Have headspace checked by a gunsmith before firing any rifle of unknown history.
Surplus ammunition of this era is frequently corrosively primed. Clean with a water-based solvent the same day you shoot.
Newly imported rifles are often packed in cosmoline throughout, including the bolt and firing pin channel. Clean it out before firing — a firing pin held forward by congealed grease causes slam fires.
The K31 is a STRAIGHT-PULL action. The bolt is pulled straight back and pushed straight forward — there is no bolt lift. If you try to lift the handle you will be working against a mechanism that does not do that.
The straight-pull bolt uses a rotating sleeve and lugs inside the bolt body to lock. It is more intricate than a turn-bolt and its disassembly is not casual work.
Swiss GP11 surplus ammunition is generally non-corrosive and of famously high quality, which is unusual for surplus. Other 7.5x55mm loadings may not be.
These rifles are frequently found in excellent condition with matching numbers, and many still carry the original owner’s name tag under the buttplate. Treat one as a collectible before treating it as a shooter.

Under spring tension

Mainspring inside the bolt
Magazine follower spring

Easily lost parts

Bolt components · Firing pin · Extractor · Floorplate components

Dry fireAvoid dry firing this firearm without snap caps. Firing pins and springs for surplus rifles are increasingly scarce. Use snap caps.

Tools

Tool	Required	Used for	Substitute
Bore guide	Yes	Cleaning from the breech without wearing the throat or the crown. On a surplus rifle the crown is often the difference between accuracy and none.

Shop difficulty

Shop tier 1 Tier 1 — easy among rifles and carbines, for the full job: strip to the parts that get coated and put it back together working. Few parts. The barrelled action comes out of the stock after the bands and two screws, and the straight-pull bolt splits into four sub-assemblies by hand. The bolt handle lug carries the striker spring, so bolt reassembly is the only fiddly step, and I found no source reporting it as a trap.

No sourced part count yet.

Bench time: about 35 min to strip, 50 min to rebuild (estimate). Bands and stock screws, straight-pull bolt into its four sub-assemblies, magazine, trigger, sights.

What comes off for coating

Stock: barrel bands, handguard, front and rear receiver screws, buttplate
Bolt: bolt handle/rail, locking collar, bolt head and extractor, firing pin assembly and spring, cocking ring
Receiver: trigger and sear, magazine catch, rear sight

Special tools

hollow-ground screwdrivers — Military screws

Known pain points

The bolt handle's lug rides in the locking collar's helical slot and compresses the striker spring. Reassembling the bolt means seating that lug against spring load in the right slot. (reassembly)
Source: A look inside the Swiss K31 Bolt — The Firearm Blog thefirearmblog.com [2] — “When retracted, the bolt handle’s square lug compresses the striker spring and its round center slides in the helical channel of the collar”

Fit or check on rebuild

Bolt locks and cocks — The handle lug has to be correctly seated in the collar cam. Standard check, not sourced.
Re-zero sights or scope — Sights and optics come off for coating, and point of impact must be re-confirmed. This is a standard check, so no source.

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.
Press the magazine catch and remove the magazine.
Removed at this step: Magazine
Pull the bolt straight rearward to extract and eject any chambered round.
Inspect the chamber and magazine well with a light and physically confirm the chamber is empty.
WarningStraight-pull or not, the chamber check is the same.
Remove all live ammunition from the work area.

Field Strip — Bolt Removal

Field Strip

Bolt removal is the whole of routine maintenance. The bore cleans from the breech with the bolt out.

Complete the Clear and Make Safe procedure.
Pull the bolt straight rearward to its rearmost position.
Press the bolt release catch on the left rear of the receiver and withdraw the bolt straight rearward out of the action.
WarningDo not attempt to rotate the bolt handle. This is a straight-pull.
Removed at this step: Bolt assembly
Clean the bore from the breech using a bore guide, and clean the bolt face, lugs, and chamber.
WarningAlways use a bore guide on a surplus rifle. Cleaning rod wear at the crown is a permanent accuracy loss and is very common on milsurp.
Stop here for routine maintenance. Bolt disassembly is a separate procedure and is not part of normal cleaning.

Reassembly

Align the bolt with the receiver raceway.
Slide the bolt straight forward into the receiver until it passes the release catch.
Cycle the bolt straight back and forward several times to confirm smooth travel and correct locking.
Reinstall the magazine and 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.

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 rifle is unloaded — chamber and magazine — before each check.
Cycle the bolt and confirm it cocks and closes fully into battery.
With the action cocked, engage the safety and press the trigger. The striker must not release.
Disengage the safety without touching the trigger. The striker must not release.
Press the trigger and confirm the striker releases with a firm snap.
Load dummy rounds and confirm they feed and eject cleanly.
If you have any doubt about the rifle’s history, have headspace gauged by a gunsmith before firing live ammunition.
Confirm the bolt locks positively at the end of its forward stroke — on a straight-pull the locking happens as you push the handle home, and it should feel definite.

Maintenance

Lubrication points

Bolt lugs and raceways
Cocking cam surfaces
Extractor
Trigger and sear contact

Cleaning notes

Surplus ammunition of this era is frequently corrosively primed. After shooting it, flush the bore, bolt face, and gas system with hot soapy water or a water-based solvent the same day, dry completely, then oil. Keep the firing pin channel clean and dry — a pin held forward by congealed cosmoline causes slam fires.

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

Wear parts to inspect

Firing pin and its protrusion · Extractor · Bolt lugs · Crown (inspect for cleaning rod wear) · Magazine follower and spring

Common issues

Symptom	Likely cause	What to do
Light strikes or misfires	Cosmoline-packed firing pin channel or a weak mainspring	Strip the bolt, clean the firing pin channel completely, and reassemble dry.
Sticky bolt lift after firing	Dirty chamber, lacquered surplus ammunition, or excessive headspace	Clean the chamber thoroughly. If it persists, have headspace checked. see a gunsmith
Rust appearing days after shooting	Corrosive primer residue	Clean with a water-based solvent the same day, dry, and oil.

Also covers

The procedures above are reported to apply to: Schmidt-Rubin Model 1911 rifle and carbine (longer action, same straight-pull principle). Verify against the manual for your specific model.

Similar manual of arms

Sourcing

Confidence: medium — Drawn from reliable secondary sources and consistent across references, but not confirmed against a primary source.
Verification: Community reviewed only
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] Karabiner 31 Handbook — Swiss Army military technical manual primary source
[2] A look inside the Swiss K31 Bolt — The Firearm Blog website secondary source
https://www.thefirearmblog.com/blog/2013/08/28/swiss-k31-bolt/ (checked 2026-10-29)

Notes: The straight-pull action is the distinctive feature and the thing that surprises people used to turn-bolts. Bolt disassembly is deliberately not described here — the rotating sleeve and lug arrangement inside the bolt is intricate and best left alone unless you have a diagram.

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