S&W Model 1940 Light Rifle Mk II
- Category
- Submachine Gun
- Barrel
- 248 mm
- Weight, empty
- 4.08 kg
- Introduced
- 1940
About
What it is, and why it matters
The S&W Model 1940 Light Rifle Mk II is a semi-automatic, blowback-operated 9x19mm submachine gun (light rifle carbine) built by Smith & Wesson for Great Britain in 1940. Firing from an open bolt and fed from a front-loading 20-round box magazine, it was an exceptionally well-machined but flawed weapon: its deeply threaded receiver cap left a thin wall that the bolt hammered against on every shot, fracturing after roughly 1,000 rounds. The Mk II replaced the Mk I's floating firing pin and bolt-mounted hammer with a fixed firing pin intended to handle hotter British military 9mm loads. Britain rejected the design and the program was cancelled, making surviving examples extremely rare.
Conceived as a quick way for Smith & Wesson to repay a British advance for a never-delivered .45 revolver contract, the Light Rifle became one of the company's costliest failures. After the British rejected and destroyed the rifles, the remaining factory stock was effectively buried until later collectors rediscovered it.
Strictly semi-automatic only despite its open-bolt, magazine-fed submachine-gun layout. Roughly 950 rifles were delivered to Britain. The fluted barrel, milled construction, and integral brass cartridge-ejection chute made it expensive and over-engineered for a wartime stopgap. The British destroyed most of their stock; a small number left at the factory were later sold in the US as Curio & Relic items.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Smith & Wesson
- Category
- Submachine Gun
- Country
- United States
- Status
- Out of production
- Produced
- 1940 to 1940
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 248 mm
- Overall length
- 813 mm
- Weight, empty
- 4.08 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Blowback
- Firing mechanism
- Open bolt
- Trigger
- Single action
- Capacity
- 20
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Steel
- Slide
- Steel
- Barrel
- Steel
- Stock
- Walnut
- Finish
- Blued
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 365 m/s
- Muzzle energy
- 481 J
- Effective range
- 100 m
Trajectory
What the round does downrange
Solved from the muzzle figures and the bullet. The dashed rule is the effective range on the record, and the crosses are the steps the solver returned.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Front loading magazine well
Fluted barrel
Milled steel construction- Integral brass cartridge chute
Standing
How it compares
Each figure against the firearms of the same type and cartridge that record it, or of the same type where that cartridge has too few. Positions are read to the nearest tenth.
| Measurement | This firearm | Median | Position |
|---|---|---|---|
| Empty weightAmong 201 9x19mm Parabellum submachine guns | 4.08 kg | 3.18 kg | Heavier than about 90% |
| Overall lengthAmong 200 9x19mm Parabellum submachine guns | 813 mm | 723 mm | Longer than about 70% |
| Barrel lengthAmong 202 9x19mm Parabellum submachine guns | 248 mm | 213 mm | Longer than about 70% |
| Magazine capacityAmong 204 9x19mm Parabellum submachine guns | 20 | 32 | Among the smallest capacities |
Answers
Questions about the S&W Model 1940 Light Rifle Mk II
How much does the S&W Model 1940 Light Rifle Mk II weigh?
The S&W Model 1940 Light Rifle Mk II weighs 4.08 kg (8.99 lb) empty.
What caliber is the S&W Model 1940 Light Rifle Mk II?
The S&W Model 1940 Light Rifle Mk II is chambered in 9x19mm Parabellum.
How many rounds does the S&W Model 1940 Light Rifle Mk II hold?
The S&W Model 1940 Light Rifle Mk II holds 20 rounds, fed from a detachable box magazine.
How long is the S&W Model 1940 Light Rifle Mk II?
The S&W Model 1940 Light Rifle Mk II is 813 mm (32.0 in) long overall, with a 248 mm (9.76 in) barrel.
Who makes the S&W Model 1940 Light Rifle Mk II?
The S&W Model 1940 Light Rifle Mk II is made by Smith & Wesson (United States).
When was the S&W Model 1940 Light Rifle Mk II introduced?
The S&W Model 1940 Light Rifle Mk II was introduced in 1940 and discontinued in 1940.
How does the S&W Model 1940 Light Rifle Mk II operate?
The S&W Model 1940 Light Rifle Mk II uses a blowback action, and its firing mechanism is open bolt.
Compatibility
Which parts fit this firearm
Studio
Every part that mounts on this, resolved
Not a list the maker typed out: the answer comes from the mounts this firearm exposes and the interface each part needs, so it stays right when either one changes.
- Every part that mounts on any firearm in the catalogue
- Interface standards, platforms and fit overrides
- The same answers through the API and the MCP server
Requires a signed-in GunSpec account on the Studio plan. The answer is computed per part, so it is not part of the public record.
Provenance
What the record holds
Every figure above was taken from one of these pages. The confidence reflects how much of the record came from a page a claim can be checked against.
In service
- British Purchasing Commission
- 1940
Provenance
Confidence in this record
78%
Stockists
Where to buy
Offers link straight to the shop. GunSpec never takes the order.
No shop has listed this firearm yet
Stock and prices come from the shops themselves. If you sell this firearm, you can list it and it appears here.
List a firearmMCP
Ask an assistant about it
The same record, reached the way a person asks for it rather than the way a program does.
Ask GunSpec
Works with
Point an MCP client at GunSpec and it answers from the catalogue rather than from memory. A free key covers the read tools.
API
The call that returns this record
The same fields, in the same units, from the same endpoint the page reads.
curl --request GET \ --url 'https://api.gunspec.io/v1/firearms/smith-mark-ii-smg' \ --header 'X-API-Key: your_key'{ "id": "smith-mark-ii-smg", "name": "S&W Model 1940 Light Rifle Mk II", "manufacturer": { "id": "smith-wesson", "name": "Smith & Wesson", "countryCode": "US", "foundedYear": 1852, "website": "https://www.smith-wesson.com", "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-02-11 23:44:40", "updatedAt": "2026-02-18 03:40:48", "version": "6e259a578cb1b21d72610d761d652c983ff25806b9e736e2db8d2938596e9202" }, "category": { "id": "submachine-gun", "name": "Submachine Gun", "description": "Automatic firearms chambered in pistol calibers" }, "country_of_origin": "US", "year_introduced": 1940, "barrel_length_mm": 248, "weight_empty_g": 4080, "action_type": "blowback"}