Mendoza HM-3
- Category
- Submachine Gun
- Barrel
- 255 mm
- Weight, empty
- 2.69 kg
- Introduced
- 1990
About
What it is, and why it matters
The Mendoza HM-3 is a compact 9x19mm Parabellum submachine gun of Mexican origin, manufactured by Productos Mendoza S.A. and put into production in the 1990s. It operates on a simple blowback principle from an open bolt, using a wrap-around bolt that extends forward over the barrel to keep the overall length short. The magazine feeds through the pistol grip, and a horizontal side-folding stock doubles as a forward grip when collapsed. A grip safety and a combined safety/fire-selector switch are provided. Owing to strict Mexican export laws, it was never officially exported and served almost exclusively with Mexican military and police forces.
The HM-3 was designed by Hector Mendoza, son of Rafael Mendoza, continuing Mexico's indigenous small-arms tradition that traces back through Rafael Mendoza's light machine guns to Manuel Mondragon's early self-loading rifles.
Reported specifications vary slightly by source: barrel length is given as 255mm (10 in) by Forgotten Weapons, while Modern Firearms lists 225mm and an overall folded length of 400mm. The combined safety/fire selector sits on the right side above the trigger. A family of variants is reported (HM-3, HM-4, HM-3 Short/Long, HM-3 Mini/Bulldog, and a semi-automatic HM-3S police carbine with closed-bolt operation and polymer furniture), but they are not catalogued separately here.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Productos Mendoza S.A.
- Category
- Submachine Gun
- Country
- Mexico
- Status
- In production
- Produced
- 1990
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 255 mm
- Overall length
- 635 mm
- Weight, empty
- 2.69 kg
- Weight, loaded
- 3.35 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
- Slide
- Steel
- Barrel
- Steel
- Stock
- Steel
BallisticsFrom the service cartridge, not a handload.
- Rate of fire
- 600 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.
Wrap around bolt
Side folding stock
Magazine in grip
Compact design
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 | 2.69 kg | 3.18 kg | Lighter than about 70% |
| Overall lengthAmong 200 9x19mm Parabellum submachine guns | 635 mm | 723 mm | Shorter than about 80% |
| Barrel lengthAmong 202 9x19mm Parabellum submachine guns | 255 mm | 213 mm | Longer than about 70% |
| Magazine capacityAmong 204 9x19mm Parabellum submachine guns | 32 | 32 | Holds more rounds than about 60% |
Answers
Questions about the Mendoza HM-3
How much does the Mendoza HM-3 weigh?
The Mendoza HM-3 weighs 2.69 kg (5.93 lb) empty and 3.35 kg (7.39 lb) loaded.
What caliber is the Mendoza HM-3?
The Mendoza HM-3 is chambered in 9x19mm Parabellum.
How many rounds does the Mendoza HM-3 hold?
The Mendoza HM-3 holds 32 rounds, fed from a detachable box magazine.
How long is the Mendoza HM-3?
The Mendoza HM-3 is 635 mm (25.0 in) long overall, with a 255 mm (10.04 in) barrel.
Who makes the Mendoza HM-3?
The Mendoza HM-3 is made by Productos Mendoza S.A. (Mexico). It was designed by Hector Mendoza.
When was the Mendoza HM-3 introduced?
The Mendoza HM-3 was introduced in 1990.
How does the Mendoza HM-3 operate?
The Mendoza HM-3 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
- Mexican Armed Forces
- Mexico
- Mexican Police Forces
- Mexico
Provenance
Confidence in this record
72%
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/mendoza-smg' \ --header 'X-API-Key: your_key'{ "id": "mendoza-smg", "name": "Mendoza HM-3", "manufacturer": { "id": "productos-mendoza", "name": "Productos Mendoza S.A.", "countryCode": "MX", "foundedYear": 1911, "website": "https://www.mendozafa.com", "logoUrl": null, "description": "Mexican firearms and air gun manufacturer founded in 1911 by Rafael Mendoza Blanco. Based in Xochimilco, Mexico City. Produces firearms including the HM-3 submachine gun used by Mexican police, semi-automatic rifles, and air guns.", "status": "active", "defunctYear": null, "stateOwned": null, "makesFirearms": true, "parentId": null, "predecessorId": null, "createdAt": "2026-06-21 23:00:46", "updatedAt": "2026-06-21 23:00:46", "version": "3a4138b1edd3f2a806f09e6c45c431d7eb2a2b130a11412e2abd4902db13cf90" }, "category": { "id": "submachine-gun", "name": "Submachine Gun", "description": "Automatic firearms chambered in pistol calibers" }, "country_of_origin": "MX", "year_introduced": 1990, "barrel_length_mm": 255, "weight_empty_g": 2690, "action_type": "blowback"}