The Ultimax 100 was designed in the late 1970s in Singapore as a lightweight squad automatic weapon. It’s a gas-operated design, with special attention paid to reducing felt recoil. The receiver is longer than most similar guns, and a carefully calibrated recoil spring prevents the bolt from contacting the back end of the receiver. We’ve not yet fired one, but by all accounts this translates the recoil impulse into a steady soft push instead of a series of impacts, and makes the weapon extremely controllable despite its light weight (under 11 pounds).
The Ultimax is also intentionally magazine-fed, instead of using belts. This was done to increase reload speed and allow more effective use by a single shooter (belt loading is usually a 2-man affair). Early variants of the Ultimax used proprietary drums, but the recent Mk IV is set up for standard AR magazines and Beta-C drums. By most accounts, the Ultimax is the premier light machine gun in existence today, and really makes the M249 SAW look clumsy. We can’t attest to that from experience, so instead we will leave you with a copy of an Ultimax Mk III technical manual (complete with exploded drawings):
(1984) Ultimax 100 MkIII manual (English)