Karabiner Modell 1931 (K31) Identification & Dating

A collector reference to Swiss K31 model recognition, military serial chronology, component agreement, private-ownership marks, and troop-tag evidence.

Two essential distinctions: the military serial sequence changes in 1953, and a military rifle later marked P is not the same category as a factory private-series rifle.

Overview
ID Checklist
K31 vs. K11
Serial Dating
Marks & Ownership
Parts & Stock
Troop Tags
Special Versions
Sources

Karabiner Modell 1931: Establishing the Model

The Swiss Karabiner Modell 1931, commonly called K31, is a straight-pull rifle associated with Waffenfabrik Bern. Swiss-language references also use Kar. 31 and the French Mousqueton 31 / Mq. 31. Its compact receiver, rear cocking ring, short bolt system, and six-round detachable magazine distinguish it within the Swiss service-rifle succession.

For an advanced identification, keep receiver production, component agreement, military ownership history, and later target modifications separate. The serial may date the receiver while a replacement stock, a private-ownership mark, or an added sight belongs to a later event.

Identification Checklist

Confirm K31 architecture before applying any Swiss serial table.
Copy the complete receiver serial, including any prefix or separately placed P.
Compare the bolt and magazine numbers individually.
Record stock wood, cartouche, repairs, and any visible component marks.
Distinguish a private-series serial from a later privatization stamp.
Keep a stock date or repair date separate from the receiver production year.
Record a troop tag as documentary evidence, including any uncertain reading.
Describe added diopter or scope equipment independently of the rifle’s identity.

Physical Identification and the K11 Comparison

Feature	K31 pattern	Comparison / significance
Action & bolt	Compact straight-pull system with rear cocking ring.	A ring is common to earlier Swiss rifles too. Compare the receiver length and the position of the chamber / magazine.
Barrel	652 mm / about 25.7 in.	The K11 has a 592 mm barrel. The K31 gains barrel length through a more compact action.
Rear sight	Tangent sight graduated 100–1,500 m.	The standard K11 scale begins at 300 m. A replaced sight must still be considered.
Magazine	Six-round detachable box magazine.	A detachable magazine alone does not distinguish K31 from every earlier Swiss model.
Service cartridge	7.5×55 mm Swiss, GP11.	Do not transfer the identification or ammunition assumptions of an earlier Swiss model simply because both have a straight-pull bolt.

When photographs are the only evidence, ask for a clear receiver-and-magazine view as well as the full rifle. A broadside silhouette can hide the very action differences that separate adjacent Swiss models. Treat the familiar commercial expression “Schmidt-Rubin” as a family shorthand, then identify the actual model.

Military-Series Serial Numbers by Year

The following reference covers the standard military production sequence. It excludes trials, special allocations, and the private series. Read the full serial before using it.

Standard military production, 1933–1958
Year	Military-series serial range
1933	520,010–521,202
1934	521,203–536,736
1935	536,737–550,400
1936	550,401–561,727
1937	561,728–573,366
1938	573,367–583,700
1939	583,701–599,000
1940	599,001–632,575
1941	632,576–686,725
1942	686,726–736,075
1943	736,076–786,550
1944	786,551–838,450
1945	838,451–864,650
1946	864,651–880,250
1947	880,251–901,200
1948	901,201–921,300
1949	921,301–936,800
1950	936,801–950,000
1951	950,001–973,050
1952	973,051–994,450
1953	994,451–999,999 and 215,001–222,450
1954	222,451–239,600
1955	239,601–250,850
1956	250,851–257,250
1957	257,251–260,200
1958	260,201–263,330

Ranges reproduced as factual reference data from the published table at K31.ch, adapted there from Reinhart, Sallaz, and am Rhyn, Die Repetiergewehre der Schweiz.

The important sequence change: military numbering reached 999,999 in 1953 and then continued at 215,001. A K31 in the 220,000 range is consequently later than one in the 900,000 range. Do not sort the entire production run by numerical size alone.

These are year-level assignments, not shipment dates or proof of first issue. An unfamiliar prefix, a trial number, or a serial outside these blocks calls for the appropriate separate register. A number matching the table still identifies only the numbered component until the rest of the rifle is compared.

Acceptance, Privatization, and Private-Series Rifles

Mark / evidence	Interpretation	Collector limit
Swiss cross and small inspection marks	Acceptance and component-inspection evidence in the appropriate marking group.	Record each symbol’s exact form and location; not every small letter is a unit abbreviation.
A separately applied P	Commonly associated with transfer of a military rifle to private ownership.	The P does not change the receiver’s original manufacture year.
P as part of a private-series serial	A rifle made in the separate private sequence, rather than an ordinary military serial subsequently privatized.	Use the private-series register, not the military table above.
P followed by a year, where present	Can document the privatization event.	It should not be silently substituted for the receiver production year.
Importer, retailer, or later proof marks	Evidence of a later commercial or regulatory stage.	They do not replace the Swiss manufacturing or acceptance history.

The placement and relationship of the P to the number matter. Photograph the entire area rather than cropping to the letter, and preserve spacing in the transcription. A statement that the rifle was “privately owned” is not, by itself, a claim that it was manufactured in the private series.

Number Agreement, Wood, and Component Dates

Compare receiver, bolt, and magazine numbers as separate entries. If the wood is examined during appropriate conservation or qualified inspection, record stock and handguard numbering as well. Describe the parts actually checked: “receiver, bolt, and magazine agree” is more precise than “all matching” when the wood has not been examined.

Walnut is associated with earlier production and beech became standard during 1946; published chronology places the change at serial 868,901. That is a production clue, not a rule proving that a particular stock has never been replaced.

A lighter stock is not automatically beech, and a dark finish does not prove walnut. Grain and structure are stronger evidence than color. When a stock date differs from the serial-table year, retain both readings before deciding whether the difference reflects component storage, replacement, or repair.

Material codes such as +CN and +CM distinguish chromium-nickel and chromium-molybdenum steel on relevant components. Published chronology associates the temporary CM substitution with 1944. These identify material and production context, not an independent date for the complete rifle.

Three useful catalog fields: receiver year; numbered parts inspected and their agreement; stock identity and date evidence. These can be completed independently, leaving an unknown explicit instead of forcing everything into one year.

Troop Tags: Useful Evidence with Practical Limits

A paper identification slip may survive beneath the buttplate. Typical entries identify a soldier, year of birth, unit, and residence or service locality. The form and completeness vary. A surviving tag can make a rifle’s history more personal, but it should be transcribed with the same care as the metal markings.

Keep the original wording, line breaks, abbreviations, and uncertain characters in the research record before preparing a translation. A birth year is not a rifle manufacture date. A named unit is not evidence that the rifle accompanied the soldier at every posting.

Unless independently corroborated, describe the slip as “found beneath the buttplate” or “associated troop tag.” Avoid turning it into an uninterrupted provenance claim. An absent tag does not disprove military service, and a tag can survive in replacement furniture.

Target Sights, Scopes, and Special Versions

Swiss military documentation treats the scoped 31/42 and 31/43 as distinct versions with their own optical equipment. A standard K31 fitted with a later scope mount or target sight should therefore be described as an equipped or modified K31 until the evidence supports a particular special version.

Inspect the sight’s maker, markings, attachment, and relation to the receiver. Record whether the evidence supports an original military configuration, later organized target use, or a recent accessory installation. A useful aftermarket sight can be collectible in its own right without changing the manufacturing identity of the rifle below it.

Sources & Further Research

Use the military manual for model features and the appropriate serial register for the number category. Component dates, ownership dates, and tag dates answer different questions.

Swiss Army, Regulation 53.101d: Der Karabiner (1961) — Scanned original manual; K11 / K31 comparison and the scoped 31/42 and 31/43 patterns.
K31.ch: Serial Numbers and Manufacturing Dates — Published production table, special-number categories, and stock-change chronology; source publication identified on that page.
Swiss Rifles: Swiss Rifle Markings — Illustrated acceptance, repair, and ownership-mark comparisons.
Swisswaffen: Privatization Markings on Swiss Rifles — Photographed distinction between later military privatization marks and original private-series numbers.
Swiss Rifles: K31 Identification Tags — Typical tag fields and transcription context.

Descriptions concern standard patterns and documented variations; an individual rifle may retain evidence from several periods.

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