Ultimax 100

Lore & Background

The Ultimax 100 was developed by a team of engineers at CIS under the direction of American firearms designer L. James Sullivan, with work starting in 1978. The weapon is gas-operated, firing from an open bolt with a rotating bolt containing seven locking lugs. Its defining feature is the constant-recoil principle, where the bolt carrier group travels rearward without impacting the rear, stopping gradually against the return springs, resulting in low recoil. The weapon is striker-fired and has a non-reciprocating cocking handle on the left side of the receiver.

The Ultimax 100 feeds from a proprietary 100-round synthetic drum magazine (early models also used 60-round drums) or from modified 20- or 30-round STANAG 4179 magazines. The drum magazine was bulky and difficult to reload without a special mechanism, and the machine gunner could not take magazines from squad members equipped with M16s. M16 magazines were modified by drilling two holes at the left feeding lip for use with the production model. The Mark 4 version submitted for the USMC Infantry Automatic Rifle competition used only STANAG magazines, losing the drum; the Mark 5 rectified this by allowing the Beta C-Mag.

The Mark 3 variant is used by the Singapore Armed Forces as a support arm, classified and known as the SAW (Section Automatic Weapon). It features a quick-change barrel, a three-position gas regulator, an adjustable bipod, and an aperture rear sight graduated to 1,200 m. The weapon's ergonomics are similar to the Thompson submachine gun, particularly the forward grip. It can mount an M16-type bayonet and day or night optics.

Reader's Guide

The Ultimax 100's significance lies in its combination of light weight, accuracy, and low recoil, achieved through the constant-recoil system. This design allowed the weapon to be used effectively even without the buttstock, relying only on the pistol and forward grips. However, its widespread adoption was compromised by its feed system. The original 100-round drum magazine was bulky and difficult to reload, and the machine gunner could not share magazines with M16-armed squad members. While M16 magazines were later modified for use, the drum remained a limitation. The weapon was submitted for the USMC Infantry Automatic Rifle program but was not selected; the Marine Corps chose an automatic rifle based on the HK416. The Ultimax 100 has been used by the armed forces of Singapore, Croatia, the Philippines, and others, including US Army Special Forces and Delta Force. It has undergone several variants, including the Mark 8 unveiled at the 2012 Singapore Airshow and a belt-fed Mark 9. The Singapore Army, which commissioned the weapon in 1982, will gradually replace it with the Colt IAR6940E-SG.

Did You Know?

• The weapon's constant-recoil system allows the bolt carrier group to travel rearward without impacting the rear of the receiver.
• The Mark 3 variant is known in the Singapore Armed Forces as the SAW (Section Automatic Weapon).
• The Ultimax 100 was designed to feed from magazines rather than belts, an unusual feature among modern machine guns.