Welgun
- Category
- Submachine Gun
- Barrel
- 200 mm
- Weight, empty
- 3.10 kg
- Introduced
- 1942
About
What it is, and why it matters
The Welgun is a British prototype submachine gun developed during the Second World War by the Special Operations Executive (SOE) at its Station IX research facility near Welwyn Garden City, with engineering and manufacturing input from the Birmingham Small Arms Company. Chambered in 9x19mm Parabellum, it used a simple blowback action firing from an open bolt with a wrap-around bolt that telescoped over the barrel to keep the weapon short and compact. It fed from standard 32-round Sten magazines, fired at roughly 500 rounds per minute, and featured a folding stock for concealment and air-drop to resistance fighters. Despite performing well in trials and proving notably accurate, the cheaper Sten was retained and the Welgun never entered series production.
The Welgun took its name from Welwyn, home of SOE's Station IX, the clandestine research lab that also produced the Welrod silent pistol and Welbike folding paratrooper motorcycle. Compact and air-droppable, it was intended to arm resistance fighters and special forces, but lost out to the mass-produced Sten despite being praised as a superior weapon in trials.
Only a small number of prototypes were built, with around six examples produced at Station IX by 1942 for demonstration. The Welgun was found to be the most accurate weapon at 250 yards in comparative trials but failed cold-weather testing. A planned requirement for 100,000 units at 5,000 per month never materialised because the Sten Mk IV was adopted instead.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Birmingham Small Arms Company
- Category
- Submachine Gun
- Country
- United Kingdom
- Status
- Prototype
- Produced
- 1942 to 1943
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 200 mm
- Overall length
- 700 mm
- Weight, empty
- 3.10 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Blowback
- Firing mechanism
- Open bolt
- Capacity
- 32
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Steel
- Barrel
- Steel
- Stock
- Steel
- Finish
- Blued
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 365 m/s
- Effective range
- 100 m
- Rate of fire
- 500 rpm
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.
Folding stock
Compact design
Wrap around bolt
Dust cover
Sten magazine compatible
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 | 3.10 kg | 3.18 kg | Near the median |
| Overall lengthAmong 200 9x19mm Parabellum submachine guns | 700 mm | 723 mm | Shorter than about 60% |
| Barrel lengthAmong 202 9x19mm Parabellum submachine guns | 200 mm | 213 mm | Shorter than about 60% |
| Magazine capacityAmong 204 9x19mm Parabellum submachine guns | 32 | 32 | Holds more rounds than about 60% |
Answers
Questions about the Welgun
How much does the Welgun weigh?
The Welgun weighs 3.10 kg (6.83 lb) empty.
What caliber is the Welgun?
The Welgun is chambered in 9x19mm Parabellum.
How many rounds does the Welgun hold?
The Welgun holds 32 rounds, fed from a detachable box magazine.
How long is the Welgun?
The Welgun is 700 mm (27.6 in) long overall, with a 200 mm (7.87 in) barrel.
Who makes the Welgun?
The Welgun is made by Birmingham Small Arms Company (United Kingdom). It was designed by Station IX / Birmingham Small Arms.
When was the Welgun introduced?
The Welgun was introduced in 1942 and discontinued in 1943.
How does the Welgun operate?
The Welgun 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
- Special Operations Executive
- United Kingdom
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/bsa-welgun' \ --header 'X-API-Key: your_key'{ "id": "bsa-welgun", "name": "Welgun", "manufacturer": { "id": "birmingham-small-arms", "name": "Birmingham Small Arms Company", "countryCode": "GB", "foundedYear": 1861, "website": null, "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-04-26 23:12:00", "updatedAt": "2026-04-26 23:12:00", "version": "ae6e88d593a8c089b8f2f2f6e564f2eef2056d641dd74def2ac44494b3a5930b" }, "category": { "id": "submachine-gun", "name": "Submachine Gun", "description": "Automatic firearms chambered in pistol calibers" }, "country_of_origin": "GB", "year_introduced": 1942, "barrel_length_mm": 200, "weight_empty_g": 3100, "action_type": "blowback"}