Since we looked at the final (for now) evolution of the venerable Browning 1919 this week, I thought I would also discuss one of the most interesting new (ish) developments in machine guns as well.
This is the Ultimax 100 from The Charted Industries of Singapore. It is a 5.56NATO chambered light machine gun/section support weapon depending on which nomenclature you prefer. It can be fed from a proprietary 100 round drum or 30 round box magazines (Mk 4 and Mk 5 versions accept M16-type mags). The number one difference between the Ultimax and other LMGs is weight. The Ultimax weighs in at about 10.5 pounds (unloaded) compared to the FN Minimi (M249 in US service) at about 17 pounds and the Israeli Negev LMG at 16.5 pounds.
Now there are problems associated with drum magazines. They are almost always expensive, they are bulky (even when empty), some are brittle, most rattle fairly loudly and many have reliability issues. Of course, many box magazines have reliability issues too. The ammo load for a SAW gunner can be between 600-1200 rounds. It would be very difficult to impossible to carry 12 drum mags and even if you could, you wouldn't be climbing mountains, jumping in and out of vehicles or climbing walls. At least not very quickly.
The Ultimax is also said to have a much lower felt recoil than would be expected due to the fact that it uses a constant recoil mechanism. The way that works is that the bolt carrier group travels rearward during the cycle, but never impacts the rear of the receiver. Instead of the jarring impact of metal on metal at hundreds of feet per second, the bolt group is slowly stopped by the action springs. This combined with the balance of the weapon make it very easy to shoot accurately, even at a rate of fire around 600 rounds per minute. With a raked pistol grip and forward grip, the ergonomics have been compared to the Thompson submachine gun. It is a full auto only weapon that uses a striker fired system and fires from the open bolt position to facilitate barrel cooling during auto fire. Most of the variants have a quick change barrel which is vital to any weapon designed for support fire. The cocking lever is on the left side and does not reciprocate when the weapon is fired. The Ultimax has a adjustable bipod and can be fitted with M16 style bayonets and also specialized day or night sights. The buttstock is removable, but in my opinion, the lost accuracy would not be worth the reduction of weight and length.
Here is a video of the Ultimax 100 being fired. Notice the almost complete lack of muzzle rise and the ease in which it is fired. And, I'm not trying to be mean here, but that guy isn't exactly Rambo.
While the design of the Ultimax was completed in 1977 and it has been in service since the early 1980's, it has recently been the focus of several Western Armed Forces, including the USMC. The USMC is currently running the Infantry Automatic Rifle Program for a weapon to replace some of the M249 light machine guns in their squads. The main design deficiency of the M249 in the eyes of the Corps is its weight. Also in competition against the Ultimax 100 are entries from H&K, FN and Colt Defense. (The Ultimax is pretty much not going to win though, despite its many advantages)