Ultimax 100

The Ultimax 100 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 seven 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.{{cite web|url=http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=4475438|title=(United States Patent: 4,475,438) Gas operated, automatic or semi-automatic guns|last=L. James Sullivan|author-link=L. James Sullivan|date=9 October 1984|publisher=United States Patent and Trademark Office|access-date=8 May 2011|archive-url=https://web.archive.org/web/20180118123921/http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=4475438|archive-date=18 January 2018|url-status=live}} Jane's International Defence Review correspondent—Andrew Tillman, in an exclusive invitation from ST Kinetics to participate in the Product Improvement Program (PIP, initiated in 1989) to test fire the gun, elaborated:Andrew, pp. 1095.

{{quotation|This article began by praising the Ultimax for its ease of control, which allows accurate fire. A comment to the author by an experienced SEAL team leader aptly underlines the importance of having an accurate light machine gun: "Men react one of two ways when they are shot at. If you just shoot at them, they will take cover and return fire, but if you start hitting them, they withdraw."}}

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). An unusual feature among modern machine guns is the fact the Ultimax was purposely designed to feed from magazines as opposed to belts.

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{{Cite web|url=https://modernfirearms.net/en/machineguns/singapore-machineguns/stk-ultimax-100-eng/|title=STK Ultimax 100|date=27 October 2010|website=Modern Firearms|access-date=3 June 2021|archive-date=13 April 2021|archive-url=https://web.archive.org/web/20210413224558/https://modernfirearms.net/en/machineguns/singapore-machineguns/stk-ultimax-100-eng/|url-status=live}} and either day or night-time optics. The Ultimax 100's ergonomics are similar to that of the Thompson submachine gun, specifically the forward grip.

Widespread adoption of the design might have been compromised by its feed system. The original Ultimax 100 was meant to be used with a drum magazine holding 100 rounds. The drum magazine was bulky and difficult to reload without a special mechanism. The shape of the drum magazine also occupied more space compared to M16 magazines or the FN Minimi box holding a belt of 200 rounds. The machine gunner also could not take magazines from other squad members who were equipped with M16s.

M16 magazines were subsequently modified to allow them to be used with the production model Ultimax 100. This was done by drilling two holes right at the left feeding lip of the magazine. This improved the handiness of the weapon and allowed magazines to be loaded in the field.

The system was modified to use only STANAG compatible magazines in the Mk 4 version of the design, which was submitted for the USMC Infantry Automatic Rifle competition. This meant the original drum could no longer be used, making the design closer to the IAR than a light machine gun. This has been rectified in the latest Mk 5 variant which allows the usage of the Beta C-Mag.

• Mark 1: Model with a quick-change barrel (pre-production).
• Mark 2: Equipped with a fixed barrel.
• Mark 3/3A: Quick-change barrel. 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. There is also an optional {{convert|10.5|in|mm|adj=on}} VIP protection barrel. 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 five-position gas adjustment valve) that allows the rate of fire to be controlled and enables reliable operation in various environmental conditions.{{cite web |url=http://www.ultimaxsaw.com/History.html |title=Ultimax 100 History |access-date=11 November 2008 |url-status=usurped |archive-url=https://web.archive.org/web/20080802190340/http://www.ultimaxsaw.com/History.html |archive-date=2 August 2008 }} 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.{{citation needed|date=March 2013}} 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 an impact-resistant polymer.{{cite web |url=http://www.ultimaxsaw.com/Ultimax%20100%20Models.html |title=Ultimax 100 MK3 |access-date=11 November 2008 |url-status=usurped |archive-url=https://web.archive.org/web/20080802190216/http://www.ultimaxsaw.com/Ultimax%20100%20Models.html |archive-date=2 August 2008 }}{{cite web |url=http://www.stengg.com/upload/194X9nI4kMKCDKfW7kd.pdf |title=Ultimax 100 Brochure |access-date=11 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20120204131243/http://www.stengg.com/upload/194X9nI4kMKCDKfW7kd.pdf |archive-date=4 February 2012 }} The Mark 3/3A can fire both the American 5.56×45mm M193 cartridge (with 1:12 (305 mm) twist barrel fitted) or the heavier SS109/M855 cartridge (178 mm (1:7 in) twist rate barrel).
• Mark 4: Developed for the United States Marine Corps Infantry Automatic Rifle program, with the addition of a new fire selector module. The Marine Corps did not select the Ultimax and chose an automatic rifle based on the HK416.{{cite web|url=http://www.defensereview.com/us-marine-corps-selects-hk-iar-infantry-automatic-rifle-as-replacement-for-fn-m249-sawlmg|title=U.S. Marine Corps Selects Heckler & Koch Infantry Automatic Rifle (HK IAR) Candidate as Replacement for FN M249 SAW/LMG|last=Crane|first=David|date=4 December 2009|publisher=defensereview.com|access-date=20 August 2010|archive-url=https://archive.today/20120729041708/http://www.defensereview.com/us-marine-corps-selects-hk-iar-infantry-automatic-rifle-as-replacement-for-fn-m249-sawlmg|archive-date=29 July 2012|url-status=live}}
• Mark 5: Updated variant of the Mark 4 with a folding stock, Picatinny rails and M16 STANAG 4179 magazine well that will accept 30-round box magazines and the 100-round Beta C-Mag drum.{{Cite web|title="Newsweek" Attempts to Rebrand Gun Control Scheme as "Gun Safety" Cause: Tina Brown Gets Cute, Right Out of the Gate.|url=http://www.defensereview.com/newsweek-attempts-to-rebrand-gun-control-scheme-as-gun-safety-cause-tina-brown-gets-cute-right-out-of-the-gate/|access-date=27 February 2021|website=Defense Review|language=en-US|archive-date=18 December 2020|archive-url=https://web.archive.org/web/20201218063044/https://www.defensereview.com/newsweek-attempts-to-rebrand-gun-control-scheme-as-gun-safety-cause-tina-brown-gets-cute-right-out-of-the-gate/|url-status=live}}
• STK also developed a vehicle-mounted variant of the weapon for use on the Bronco All Terrain Tracked Carrier{{cite web |url=http://intelweb.janes.com/public/intelweb/index.shtml |title=New All Terrain Vehicle Makes Tracks For Eurosatory |author=Christopher F Foss |access-date=26 September 2009 |date=20 June 2000 |publisher=Jane's Daily (subscription required to access) |url-status=dead |archive-url=https://web.archive.org/web/20091227150939/http://intelweb.janes.com/public/intelweb/index.shtml |archive-date=27 December 2009 }} and on the Spider Light Strike Vehicle.{{cite web|url=http://www.army-technology.com/projects/spider_light_strike/|title=Spider Light Strike Vehicle, Singapore|publisher=Army-Technology.Com|access-date=7 February 2011|archive-url=https://web.archive.org/web/20101221154119/http://www.army-technology.com/projects/spider_light_strike/|archive-date=21 December 2010|url-status=live}}{{Unreliable source?|reason=domain on WP:BLACKLIST|date=June 2016}}
• Mark 8: New variant unveiled at the 2012 Singapore Airshow.{{cite web |url=http://www.thefirearmblog.com/blog/2012/02/21/stk-ultimax-100-mk-8/ |title=STK Ultimax 100 MK 8 |date=21 February 2012 |access-date=12 March 2017 |archive-url=https://web.archive.org/web/20170428050927/http://www.thefirearmblog.com/blog/2012/02/21/stk-ultimax-100-mk-8 |archive-date=28 April 2017 |url-status=live }}

• {{Flag|Bosnia & Herzegovina}}{{cite web|title=Bosnia Herzegovina Land Forces military equipment, armament and vehicles Army|url=http://www.armyrecognition.com/bosnia_herzegovina_army_land_ground_forces_uk/bosnia_herzegovina_army_land_ground_armed_defense_forces_military_equipment_armored_vehicle_uk.html|url-status=live|archive-url=https://web.archive.org/web/20180925033910/http://www.armyrecognition.com/bosnia_herzegovina_army_land_ground_forces_uk/bosnia_herzegovina_army_land_ground_armed_defense_forces_military_equipment_armored_vehicle_uk.html|archive-date=25 September 2018|access-date=16 October 2014|publisher=armyrecognition.com}}
• {{Flag|Brunei}}: Adopted to replace Colt M16 HBAR LMGs.{{cite web |url=http://www.mindef.gov.bn/new_home/news2007/1-6%20Sign%20Contract%20MINDEF.htm |title=MINISTRY OF DEFENCE SIGNS CONTRACT FOR THE ULTIMAX-100 LIGHT MACHINE GUN |access-date=11 November 2008 |date=7 June 2007 |publisher=Brunei Ministry of Defence |url-status=dead |archive-url=https://web.archive.org/web/20120214173747/http://www.mindef.gov.bn/new_home/news2007/1-6%20Sign%20Contract%20MINDEF.htm |archive-date=14 February 2012 }}
• {{Flag|Chile}}: Chilean Marine Corps, replaced in 2014 by the Heckler & Koch MG4.{{cite web |url=https://www.infodefensa.com/texto-diario/mostrar/3077421/infanteria-marina-chile-exhibe-concon-modernos-fusiles-ametralladoras |title=The Chilean Marine Infantry exhibits its most modern rifles and machine guns in Concón |last=García |first=Nicolás |date=1 July 2017 |website=Infodefensa.com |access-date=23 July 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715023117/https://www.infodefensa.com/texto-diario/mostrar/3077421/infanteria-marina-chile-exhibe-concon-modernos-fusiles-ametralladoras |url-status=live }}
• {{Flag|Croatia}}
• {{Flag|Fiji}}
• {{Flag|Indonesia}}: Komando Pasukan Katak (Kopaska) tactical diver group and Komando Pasukan Khusus (Kopassus) special forces group.{{cite web |url=http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1612007/ind.asp |title=Kopassus & Kopaska - Specijalne Postrojbe Republike Indonezije |language=hr |publisher=Hrvatski Vojnik Magazine |access-date=12 June 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100822145526/http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1612007/ind.asp |archive-date=22 August 2010 }}
• {{Flag|Papua New Guinea}}
• {{Flag|Peru}}Richard J, 2009/2010.
• {{Flag|Philippines}}
• {{Flag|Serbia}}: Used by the SAJ.{{Cite web |url=https://specijalne-jedinice.com/Srbija/SAJ-English.html#sthash.H0GnUwyq.dpbs |title=Specijalne-jedinice.com {{!}} Special Anti-terrorist Unit-SAU |access-date=22 August 2018 |archive-url=https://web.archive.org/web/20180722213534/https://specijalne-jedinice.com/Srbija/SAJ-English.html#sthash.H0GnUwyq.dpbs |archive-date=22 July 2018 |url-status=live }}
• {{Flag|Singapore}}: Commissioned by the Singapore Army in 1982.{{cite web|url=http://www.mindef.gov.sg/imindef/about_us/history/maturing_saf/v12no6_history.html|title=Maximum Firepower: The Machine Guns of the SAF|access-date=11 November 2008|publisher=Singaporean Ministry of Defence|archive-url=https://archive.today/20120804232306/http://www.mindef.gov.sg/imindef/about_us/history/maturing_saf/v12no6_history.html|archive-date=4 August 2012|url-status=live}} It will gradually be replaced by the Colt IAR6940E-SG.{{Cite news |last=Yeo |first=Mike |date=21 May 2024 |title=New light machine gun for Singapore Army enters service |url=https://www.straitstimes.com/singapore/new-light-machine-gun-for-singapore-army-enters-service |access-date=1 September 2024 |work=The Straits Times |language=en |issn=0585-3923 |archive-date=9 October 2024 |archive-url=https://web.archive.org/web/20241009211526/https://www.straitstimes.com/singapore/new-light-machine-gun-for-singapore-army-enters-service |url-status=live }}
• {{Flag|Slovenia}}: Used by the Specialna Enota Policije.{{Cite web |url=https://specijalne-jedinice.com/Inostranstvo/Region/Specijalna-jedinica-policije-Republike-Slovenije-English.html#sthash.LGnIJ99k.dpbs |title=Specijalne-jedinice.com {{!}} Special Police Unit of the Republic of Slovenia |access-date=22 August 2018 |archive-url=https://web.archive.org/web/20180822181331/https://specijalne-jedinice.com/Inostranstvo/Region/Specijalna-jedinica-policije-Republike-Slovenije-English.html#sthash.LGnIJ99k.dpbs |archive-date=22 August 2018 |url-status=live }}
• {{Flag|Solomon Islands}}: Royal Solomon Islands Police Force purchased 50.
• {{Flag|Thailand}}
• {{Flag|United States}}: Known to be used by US Army Special Forces and Delta Force operators.{{Cite web|date=30 September 2016|title=US Special Forces Ultimax LMG -|url=https://www.thefirearmblog.com/blog/2016/09/30/us-special-forces-ultimax-lmg/|access-date=27 February 2021|website=The Firearm Blog|language=en-US|archive-date=18 January 2021|archive-url=https://web.archive.org/web/20210118133301/https://www.thefirearmblog.com/blog/2016/09/30/us-special-forces-ultimax-lmg/|url-status=live}}
• {{Flag|Zimbabwe}}

• {{Flagicon image|Flag of the KNLA.svg}} Karen National Liberation Army{{Cite web|date=11 December 2019|title=Trade Update 2019: Transfers, Transparency, and South-east Asia Spotlight|url=http://www.smallarmssurvey.org/fileadmin/docs/S-Trade-Update/SAS-Trade-Update-2019.pdf|url-status=dead|access-date=27 February 2021|archive-url=https://web.archive.org/web/20191211191444/http://www.smallarmssurvey.org/fileadmin/docs/S-Trade-Update/SAS-Trade-Update-2019.pdf|archive-date=11 December 2019}}
• New People's Army{{Cite web|date=18 May 2020|title=Army seize machine gun after a clash in Bukidnon|url=https://mindanaogoldstardaily.com/army-seize-machine-gun-after-a-clash-in-bukidnon/|access-date=27 February 2021|website=Mindanao Gold Star Daily|language=en-US|archiveurl=https://web.archive.org/web/20230605235925/https://mindanaogoldstardaily.com/archives/113503|archive-date=5 June 2023}}
• {{Flagicon image|Tamil Eelam Flag.svg}} Tamil Tigers{{Cite web|date=12 August 2018|title=Chinese Arms in LTTE Hands—Sri Lanka Guardian|url=https://www.slguardian.org/chinese-arms-in-ltte-hands/|access-date=27 February 2021|archive-url=https://web.archive.org/web/20180812083234/https://www.slguardian.org/chinese-arms-in-ltte-hands/|archive-date=12 August 2018}}

File:Ultimax 100 Users.png|Map with users of the Ultimax 100 in blue

File:Section Automatic Weapon.jpg|A Singaporean soldier with a deployed Ultimax 100 Mk 2 Section Automatic Weapon (SAW)

• {{lwc|ArmaLite AR-100}}
• {{lwc|M+G project}} – (Netherlands)
• {{lwc|Stoner 63}}
• {{lwc|STK 50MG}}

{{Reflist}}

{{Refbegin}}

• {{cite book|last1=Richard Jones|last2=Andrew White|title=Jane's Guns Recognition Guide|year=2008|publisher=HarperCollins|isbn=978-0-00-726645-6|page=399}}
• {{cite book|last1=Richard Jones|title=Jane's Infantry Weapons|orig-year=2009|year=2010|publisher=Jane's Information Group|isbn=978-0-7106-2869-5|page=?}}
• {{cite journal|last=Andrew|first=C. Tillman|date=August 1989|title=IDR test report: Ultimax light machine gun—the ultimate in controllability|journal=Jane's International Defence Review|publisher=Jane's Information Group|pages=1093–1095|issn=0020-6512}}

{{Refend}}

{{Commons category}}

• [https://web.archive.org/web/20211208094532/https://www.stengg.com/ultimax-100-mk8 ST Engineering's website for the Ultimax 100] (archive)

{{Singapore-designed weapons}}

Category:5.56×45mm NATO machine guns

Category:Firearms articles needing expert attention

Category:Machine guns of Singapore

Category:Squad automatic weapons

Category:Weapons and ammunition introduced in 1982