The Ultimax 100 is a light machine gun manufactured since 1982 by ST Kinetics (formerly Chartered Industries of Singapore) that chambers the 5.56x45mm NATO round. It is remarked for being extremely lightweight, and is the standard service support arm of the Singaporean Armed Forces.
There are two variants of the Ultimax 100 in the Rainbow Six universe. These variants are the Ultimax 100 Mark 2 and the Ultimax 100 Mark 3.
- The Ultimax 100 Mark 2 is a variant that contains a fixed barrel.
- The Ultimax 100 Mark 3 containing a quick change barrel, a removable buttstock, a carry handle, and an integrated vertical grip into the weapon's forend.
The Ultimax 100, Ultimax 100 Mark 2 and Ultimax 100 Mark 3 are categorized as light machine guns in the Rainbow Six universe.
Hailing from Singapore, the UM-100 machine gun holds the record for being the lightest 5.56 caliber machine gun in existence. Its unique constant recoil technology allows it to be fired one-handed or from the hip with minimal loss of accuracy. It uses a 100-round drum for ammunition, and can be fired with the butt detached.
- "A very mobile support weapon from Singapore with a shortened barrel and lightweight frame that increases its maneuverability. Normally the U100MK3 uses the Scope or Red Dot attachments."
— In-game description
The U100MK3 is a weapon featured in Tom Clancy's Rainbow Six: Lockdown.
In the console versions of the game, the U100MK3 is equipped with a Scope attachment by default. In the PC version of the game, the U100MK3 does not have the Scope automatically attached like in the console versions of the game.
The U100MK3 is a weapon featured in Tom Clancy's Rainbow Six: Critical Hour.
Vegas 1 & 2
The Ultimax 100 Mark 2 is a weapon that was supposed to be featured in Tom Clancy's Rainbow Six: Vegas and Tom Clancy's Rainbow Six: Vegas 2. It was later cut from the final release of both games but can be found among the files on PC.