The dramatically named Ultimax 100 is a lightweight gas operated SAW (Squad Automatic Weapon), firing 5.56x45mm rounds from an open bolt. Designed by James Sullivan in the early '80s, it has been produced from 1982 to the present day, originally by Chartered Industries of Singapore, now by Singapore Technologies Kinetics, and is used in Croatia, Honduras, Indonesia, Papua New Guinea, Peru, the Philippines and Singapore, although it has seen little 'real' use apart from anti-guerilla operations in Indonesia and the Philippines. For a feed system it uses either a modified M16-style 30-round STANAG magazine or a proprietary 100-round drum magazine, although to use a STANAG magazine two small holes must be drilled into the top left corner of the magazine, and changing the 100-round drum requires tools. Usually ships with two position safety (SAFE, AUTO) but variants have a four position safetey (SAFE, SEMI, 3 RND BURST, AUTO). The bayonet lug will accept any M16-type bayonet. A gas regulator allows the rate of fire to be varied.
The revolutionary aspect of this gun is the way it deals with recoil, using something known as the constant recoil principle. Basically, this means rather than the bolt slamming back onto the receiver, jarring your shoulder, it decreases in speed as it passes the length of the barrel.