Replaced Bolt sleeves on Model 1931 carbine (Created: 20.12.2018, Changed: 11.01.2024)
An Extended Report on Defects in the Modell 1931 Carbine Can Be Found Here, Including Source References in the Federal Archives: Defects on the Model 31 Carbine, bolt sleeves, locking piece, bayonet.
During World War II, many things in Switzerland were uncertain. No one knew if Nazi Germany would attack Switzerland, nor how long the war around them would last. Switzerland needed weapons but had limited raw materials. Consequently, various weapons experiments were conducted using other, more readily available materials.
Normally, the bolt parts of the
Modell 1931 Carbine were made from chromium-nickel steel (marked
CN) and fully hardened. However, during the war years 1943, 1944, and 1945, these parts were partially made from chromium-molybdenum steel (marked
Mo) due to material shortages and were insufficiently hardened due to material constraints. Due to mix-ups, some bolt sleeves made from CN steel were also insufficiently hardened! For the bolt sleeve (part number
T-K31-42), which locks the bolt with the locking lugs, the insufficient hardening proved too unstable, resulting in hairline cracks in the locking lugs, and in some cases, the locking lugs even broke off.
The Swiss Army recognized the problem with insufficiently hardened bolt sleeves in the serial number range between 750000 and 850000 (note by the author: probably 860000) and began replacing them during inspections or refresher courses. Unnumbered bolt sleeves were used for this purpose. Since these sleeves were already hardened in the factory, they could no longer be stamped with a number. Thus, they were numbered analogously to the weapon number using an electric engraver when replaced.
Modell 1931 Carbine from the war years (especially 1943 and 1944, but also partially 1945, serial number range 750000 to 850000 (note by the author: probably 860000)) are thus entirely original if they have a bolt sleeve numbered with an electric engraver. Weapons that still have the originally numbered chromium-molybdenum bolt sleeve (MO) installed are, of course, very interesting from a collector's perspective. When shooting, the lugs should be checked more frequently, or the sleeve should be replaced for shooting with a CN replacement sleeve from the serial number range before 750000 or after 850000 (note by the author: probably 860000).
Bolt nuts (part number
T-K31-37) and other parts of the K31 (e.g., the receiver) made of Mo steel are completely unproblematic as they are not subjected to significant stress when firing.
For safety: in general, all weapons that are used for shooting should be regularly checked for their functionality.
Modell 1931 Carbine in the serial number range 750000 to 850000 (note by the author: probably 860000) with the original bolt sleeve should be inspected at shorter intervals.
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| Modell 1931 Carbine, rifle serial 814530, manufactured 1944, bolt locking sleeve replaced and numbered using an electro-pencil | Modell 1931 Carbine, bolt locking sleeve, chromium molybdenum steel (Mo) | Modell 1931 Carbine, bolt cap, chromium molybdenum steel (Mo) | Modell 1931 Carbine, bolt locking sleeve, chrome-nickel steel (CN) | Modell 1931 Carbine, bolt cap, chrome-nickel steel (CN) |
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| Modell 1931 Carbine, bolt locking sleeve, chromium molybdenum steel (Mo) | Modell 1931 Carbine, rifle serial 785759, bolt locking sleeve, chrome-nickel steel (CN), locking lug broken | Modell 1931 Carbine, rifle serial 785759, bolt locking sleeve, chrome-nickel steel (CN), locking lug broken | Modell 1931 Carbine, rifle serial 785759, bolt locking sleeve, chrome-nickel steel (CN), locking lug broken | Modell 1931 Carbine, rifle serial 785759, bolt locking sleeve, chrome-nickel steel (CN), locking lug broken |
