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Ultimax 100
Type Light machine gun
Place of origin  Singapore
Service history
In service 1982–present
Used by See Users
Wars 1990s conflicts in the former Yugoslavia, anti-guerrilla operations in Indonesia and the Philippines, 2006 Fijian coup d'état, Solomon Islands, Afghanistan, Sri Lankan Civil War
Production history
Designer L. James Sullivan
Designed 1977
Manufacturer Chartered Industries of Singapore
Produced 1982[1][2]–present
Number built ~80,000
Variants See Variants
Weight 4.75 kg (10.47 lb) (Mark 2)
4.90 kg (10.8 lb) (Mark 3)
Length 1,030 mm (40.6 in) with buttstock / 800 mm (31.5 in) buttstock detached (Mark 2)
1,024 mm (40.3 in) with buttstock / 810 mm (31.9 in) buttstock detached (Mark 3)
Barrel length 508 mm (20.0 in) (standard)
330 mm (13.0 in) (Ultimax 100 Para)

Cartridge 5.56x45mm NATO
Action Gas-operated, rotating bolt
Rate of fire 400–600 rounds/min
Muzzle velocity 970 m/s (3,182 ft/s) (M193 cartridge)
945 m/s (3,100.4 ft/s) (SS109/M855 cartridge)
Effective range 100–1,200 m sight adjustments
Maximum range 460 m (M193 cartridge)
1,300 m (SS109/M855 cartridge)
Feed system 100-round drum or 30-round STANAG M16 box magazine
Sights Rear aperture sight and front post
472 mm (18.6 in) sight radius

The Ultimax 100 is a Singaporean 5.56 mm light machine gun, developed by the Chartered Industries of Singapore – CIS (currently incorporated into the Singapore Technologies Engineering Ltd or ST Engineering group) by a team of engineers under the guidance of American firearms designer L. James Sullivan.[2] Work on a new light support weapon for the Singapore Army began in 1978.[2] The weapon is produced by CIS (presently STK – Singapore Technologies Kinetics), initially in the Mark 1 version, later – the Mark 2, and currently, only the Mark 3 (a Mark 4 variant is being evaluated). The Ultimax 100 (also called the U 100) is used in significant numbers by the armed forces of Singapore, Croatia and the Philippines.



The Ultimax 100, also known as the "Section Machine Gun" is a gas-operated automatic weapon (capable of fully automatic fire only) with a short-stroke gas piston operating system powered by ignited powder gases diverted from the barrel through a port in the gas block. The Ultimax 100 is a locked breech weapon with a rotating bolt that contains 7 locking lugs. It fires from an open bolt position. The bolt contains both a spring extractor and a casing ejector. The weapon's non-reciprocating cocking handle is located on the left side of the receiver and occupies the forward position during firing. The Ultimax 100 is striker-fired. The feature that grants the weapon its low recoil (compared to similar light machine guns) is the "constant recoil" principle. The overall design allows the bolt carrier group to travel all the way back without ever impacting the rear, instead stopping gradually along the axis of movement against the resistance of the return springs.[3] The magazine catch consists of two tapered pins on a bar, controlled by the magazine release button. The machine gun feeds from a proprietary 100-round synthetic drum magazine (early models also used 60-round drum magazines), or from a modified 20 or 30-round STANAG 4179 magazine (from the M16 rifle).

The Ultimax 100 uses a manual safety mechanism that consists of a lever installed on the left side of the receiver (just behind the trigger) with two possible settings: "S" – indicating the weapon is safe and "F" – continuous fire. An internal safety achieved through the proper arrangement of parts and mechanisms secures against premature detonation. The light machine gun was also designed to mount an M16-type bayonet and either day or night-time optics. Ergonomics of the Ultimax 100 are somewhat close to the Thompson submachine gun.


  • Mark 1 - quick-change barrel (pre-production variant)
  • Mark 2 - fixed barrel
  • Mark 3 - quick-change barrel.[2] Currently the Mark 3 variant is available in two different barrel lengths, a standard and short. The short barrel is designed for use with paratroopers and special forces. The barrel on all versions has a slotted flash suppressor and a carrying handle used to transport the weapon and assist in barrel removal. The Ultimax Mark 3 has a three-position gas regulator (early models had a 5-position gas adjustment valve) that allows the rate of fire to be controlled and enables reliable operation in various environmental conditions.[4][2] The gas regulator is usually pre-adjusted prior to operations. Where there is sluggish operation due to fouling, the gas setting may be increased by two clicks using the provided C-tool. The weapon features a standard pistol grip, a vertical forward grip integrated into the forend and a detachable buttstock. The mild felt recoil allows the weapon to be used effectively without the buttstock, using only the pistol and forward grips to support and aim the firearm. The adjustable bipod has a height adjustment mechanism and is secured to the weapon's forend, providing stability in a sustained-fire role. The bipod is quick-detachable and can be mounted or removed without the use of tools. The Ultimax 100 features an aperture type rear sight (with range settings for distances up to 1,200 m, graduated every 100 m) placed on a sliding scale and a forward vertical post housed in the front sight base and protected by two metal tabs. The weapon incorporates sheet metal stamping and the use of synthetic components in its design. The drum magazine, buttstock, pistol grip and forend with vertical grip are all made of a impact-resistant polymer.[5][6][4] The Mark 3 can fire both the American 5.56x45mm M193 cartridge (with 1:12 (305 mm) twist barrel fitted) or the heavier Belgian SS109/M855 cartridge (178 mm (1:7 in) twist rate barrel.[6]
  • Mark 4 - developed for the United States Marine Corps Infantry Automatic Rifle program,[2] with the addition of a new fire selector module.[5] The Marine Corps did not select the Ultimax.
  • Mark 5 - updated Mark 4 with folding stock, picatinny rails and fixed M16 STANAG 4179 mag well that will accept 30-round box magazines and 100-round double-drum Beta C-Mag[7].

STK also developed a vehicle-mounted variant of the weapon for use on the Bronco All Terrain Tracked Carrier.[8]




  1. ^ Daniel Watters. "The 5.56 X 45mm: 1980-1985". Retrieved 2008-11-11.  
  2. ^ a b c d e f g "Modern Firearms' STK/CIS Ultimax 100". Retrieved 2008-11-11.  
  3. ^ US4,475,438 (PDF version) (1984-10-09) L. James Sullivan, Gas operated, automatic or semi-automatic guns.  
  4. ^ a b c "Ultimax 100 History". Retrieved 2008-11-11.  
  5. ^ a b "Ultimax 100 MK3". Retrieved 2008-11-11.  
  6. ^ a b "Ultimax 100 Brochure". Retrieved 2008-11-11.  
  7. ^ Defense Review update on Mark 5 variant
  8. ^ Christopher F Foss (2000-06-20). "New All Terrain Vehicle Makes Tracks For Eurosatory". Jane's Daily (subscription required to access). Retrieved 2009-09-26.  
  9. ^ "MINISTRY OF DEFENCE SIGNS CONTRACT FOR THE ULTIMAX-100 LIGHT MACHINE GUN". Brunei Ministry of Defence. 2007-06-07. Retrieved 2008-11-11.  
  10. ^ "World Infantry Weapons: Philippines". Retrieved 2009-05-23.  
  11. ^ "Ultimax MKII Review". Retrieved 2008-11-11.  
  12. ^ "Maximum Firepower: The Machine Guns of the SAF". Singaporean Ministry of Defence. Retrieved 2008-11-11.  


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