ST Kinetics Ultimax 100
- Category
- Machine Gun
- Barrel
- 508 mm
- Weight, empty
- 4.75 kg
- Introduced
- 1982
About
What it is, and why it matters
The Ultimax 100 is a Singaporean 5.56x45mm NATO light machine gun developed by Chartered Industries of Singapore (now ST Kinetics) in the late 1970s. Its standout feature is an unusually low felt recoil thanks to a constant-recoil operating system pioneered by designer L. James Sullivan, in which the bolt carrier never bottoms out against the rear of the receiver. The Ultimax 100 is renowned for being one of the most controllable LMGs in service, allowing accurate one-handed automatic fire.
The Ultimax 100 is so smooth in operation that ST Kinetics famously demonstrated it being fired one-handed and even with the operator holding the barrel, the recoil being closer to a 5.56mm carbine than a typical squad automatic weapon.
The constant-recoil principle was inherited from Sullivan's earlier work on the Stoner 63. The Mk9 variant, unveiled at Singapore Airshow 2024, modernizes the platform with a side-folding stock, M-LOK handguard, and improved feeding from STANAG magazines.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- ST Engineering Land Systems
- Category
- Machine Gun
- Country
- Singapore
- Status
- In production
- Produced
- 1982
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 508 mm
- Overall length
- 1030 mm
- Weight, empty
- 4.75 kg
- Weight, loaded
- 6.80 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Gas operated long stroke
- Firing mechanism
- Hammer fired
- Trigger
- Single stage
- Capacity
- 100
- Magazine
- Drum
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Steel
- Barrel
- Steel
- Stock
- Polymer
- Finish
- Phosphate
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 970 m/s
- Muzzle energy
- 1880 J
- Effective range
- 1000 m
- Maximum range
- 2000 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.
- Constant recoil operating system
Quick change barrel
Folding bipod
Carrying handle
Picatinny rail
Stanag magazine compatibility
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 27 5.56x45mm NATO machine guns | 4.75 kg | 6.35 kg | Lighter than about 80% |
| Overall lengthAmong 25 5.56x45mm NATO machine guns | 1030 mm | 1020 mm | Longer than about 70% |
| Barrel lengthAmong 26 5.56x45mm NATO machine guns | 508 mm | 465 mm | Longer than about 80% |
| Magazine capacityAmong 26 5.56x45mm NATO machine guns | 100 | 200 | Holds fewer rounds than about 70% |
Its place in the rankings
Answers
Questions about the ST Kinetics Ultimax 100
How much does the ST Kinetics Ultimax 100 weigh?
The ST Kinetics Ultimax 100 weighs 4.75 kg (10.47 lb) empty and 6.80 kg (14.99 lb) loaded. It is the 4th lightest of 27 5.56x45mm NATO machine guns in the catalogue.
What caliber is the ST Kinetics Ultimax 100?
The ST Kinetics Ultimax 100 is chambered in 5.56x45mm NATO.
How many rounds does the ST Kinetics Ultimax 100 hold?
The ST Kinetics Ultimax 100 holds 100 rounds, fed from a drum magazine.
How long is the ST Kinetics Ultimax 100?
The ST Kinetics Ultimax 100 is 1030 mm (40.6 in) long overall, with a 508 mm (20.0 in) barrel.
Who makes the ST Kinetics Ultimax 100?
The ST Kinetics Ultimax 100 is made by ST Engineering Land Systems (Singapore). It was designed by L. James Sullivan.
When was the ST Kinetics Ultimax 100 introduced?
The ST Kinetics Ultimax 100 was introduced in 1982.
How does the ST Kinetics Ultimax 100 operate?
The ST Kinetics Ultimax 100 uses a gas operated long stroke action, and its firing mechanism is hammer fired.
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
- Singapore Armed Forces
- 1982
- Royal Brunei Armed Forces
- Brunei
- Croatian Armed Forces
- Croatia
- Indonesian National Armed Forces
- Indonesia
- Peruvian Armed Forces
- Peru
- Armed Forces of the Philippines
- Philippines
- Slovenian Armed Forces
- Slovenia
- Zimbabwe Defence Forces
- Zimbabwe
Provenance
Confidence in this record
86%
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/st-kinetics-ultimax-100' \ --header 'X-API-Key: your_key'{ "id": "st-kinetics-ultimax-100", "name": "ST Kinetics Ultimax 100", "manufacturer": { "id": "st-kinetics", "name": "ST Engineering Land Systems", "countryCode": "SG", "foundedYear": 1967, "website": "https://www.stengg.com", "logoUrl": null, "description": "Singapore defense contractor specializing in armored vehicles and ground combat systems. Historically produced small arms including the Ultimax 100 light machine gun and SAR 21 bullpup rifle.", "status": "active", "defunctYear": null, "stateOwned": null, "makesFirearms": true, "parentId": null, "predecessorId": null, "createdAt": "2026-02-18 03:40:48", "updatedAt": "2026-09-15 07:19:19", "version": "60b09a84aaed1bb6ff46e4d8f29b675171e7f36c2772f1aafc8dcf4bf0262e2e" }, "category": { "id": "machine-gun", "name": "Machine Gun", "description": "Fully automatic firearms for sustained fire" }, "country_of_origin": "SG", "year_introduced": 1982, "barrel_length_mm": 508, "weight_empty_g": 4750, "action_type": "gas_operated_long_stroke"}