CIS Ultimax 100

The CIS Ultimax 100 is a singaporean light machine gun created by the CIS (Now ST Kinetics) in 1982 to equip the Singapore Army, the Ultimax 100 is also used in Croatian, Philipines and other armies.

Description
In 1978, an American small arms designer James Sullivan, a man who previously worked for Armalite and participated in design of the AR-18 assault rifle, traveled to Singapore. There he joined the small arms design team at Chartered Industries of Singapore (CIS; now Singapore Technologies Kinetics) Inc, with task to design a squad automat weapon / light machine gun that could serve as a companion to the assault rifle then in development at the same company. After about four years of development and trials, Singaporean army adopted the new squad automatic weapon, known as Ultimax 100, in 1982. Ultimax light machine gun was produced in three subsequent versions (Marks), with fourth being evaluated in USA at the time of this writing (autumn 2007). The current production version is Ultimax 100 Mark 3, which is described below. Other versions are as follows: Ultimax 100 Mk.1 was a pre-production variant. Ultimax 100 Mk.2 was the first production gun, with fixed (non-detachable) barrel and a folding carrying handle located above the center of the mass of the gun. Production ceased by late eighties, with introduction of the Ultimax 100 Mk.3.Ultimax 100 Mk.4 is an updated version of Mk.3, developed for U.S. Marine Corps “Infantry Automatic Rifle” competition. It features an updated barrel with M16A2-style flash hider, Picatinny rails on top of receiver, optional for end with additional Picatinny rails on 3-, 6- and 9-o’clock positions, and a quick-detachable magazine adaptor for unmodified M16 (STANAG) magazines. The new buttstock is of skeletonized design and folds to the side. The trigger/fire control/pistol group is a modular unit, which can produce a variety of firing modes including single shots, three-round bursts and full-automatic fire.

Ultimax 100 Mk.3 is gas operated, air cooled, magazine fed weapon. Ultimax 100 Mk.3 has quick detachable barrels, equipped with carrying handle to assist hot barrel removal. Each gun is supplied with two barrels, and additional barrels of standard (508 mm) or short (330 mm) length can be obtained from manufacturer (latest versions also available with optional 267 mm “VIP Protection” barrel). Gun is gas operated, utilizing short-stroke piston gas system, located above the barrel and fitted with manual gas regulator that has five settings. Barrel is locked using rotary bolt with multiple radial lugs. The patented “constant recoil” action is in fact a simple effort to avoid the heavy bolt group slamming against the backstop in receiver. This is done by elongating the stamped-steel receiver (and available bolt travel path) and by carefully calculating the strength of return spring. Feed is from detachable magazines only, using either proprietary 100-round drum magazines or slightly modified 30-round M16-type box magazines (modification involves an additional lock holes for Ultimax magazine catch). Drum magazines are made mostly from plastic, with translucent rear wall which permits easy check of available ammunition. Original intent was to make these drums disposable but currently these are reusable. Ejection of spent cartridges is to the right side, and ejection port is covered by spring-loaded dust cover. Firing controls include a pistol grip and a conventional rifle-type trigger; ambidextrous safety / fire selector levers are located at either side of receiver, above the pistol grip. Gun fires from open bolt only, in semi-automatic or full automatic modes. Standard furniture includes a lightweight folding bipod, attached to the gas block, short polymer forend with forward pistol grip, and a removable plastic butt (gun can be safely fired with butt removed). One somewhat unusual accessory for Ultimax 100 is a bayonet lug on the barrel, which permits attachment of a standard M16-compatible bayonet.

==Operators==
 * Brunei: Was adopted to replace Colt M16 HBAR LMGs.
 * Croatia 
 * Indonesia: Komando Pasukan Katak (Kopaska) tactical diver group and Komando Pasukan Khusus (Kopassus) special forces group.
 * Peru 
 * Philippines
 * Singapore: Commissioned by the Singapore Army in 1982.
 * Slovenia
 * Zimbabwe

==Variants==
 * Mark 1: Model with a quick-change barrel (pre-production).
 * Mark 2: Equipped with a fixed barrel.
 * Mark 3: 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 Ultimax_mk3_2.jpgs. There is also an optional 10.5 inch 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 5-position gas adjustment valve) that allows the rate of fire to be controlled and enables reliable operation in various environmental conditions. 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. 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.
 * 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.
 * 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.

==Specifications==
 * Caliber 5.56mm NATO
 * Weight 4,9 kg w/o magazine; 6,8 kg with loaded 100-round magazine and sling
 * Length  1024 mm with standard barrel and butt; 633 mm with assault barrel and no butt
 * Length of barrel 508 mm or 330 mm ('assault' barrel)
 * Feeding drum magazine 100 rounds or box magazine 30 rounds
 * Rate of fire 400-600 rounds per minute