Ultimax 100 - Variants

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 forces. There is also an optional 10.5-inch (270 mm) 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. 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 an 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.

STK also developed a vehicle-mounted variant of the weapon for use on the Bronco All Terrain Tracked Carrier and on the Spider Light Strike Vehicle.