Last year the U.S. Army announced that its Natick Soldier Center had received a request for a backpack that would carry 500 rounds of linked 7.62mm machine-gun ammunition and a sleeve that would feed that ammo to a M240 7.62mm carried by a soldier wearing the backpack. That much ammo weighs about 16 kg (35 pounds). In less than seven weeks Natick produced the requested item and called it the Ironman Ammunition Carriage System. Such a pack would not be used all the time but for situations where the longer range M240 machine-gun was needed, and there expected to be a lot of fighting, it was believed that the Ironman would be very useful.
The idea for the Ironman was first proposed by a National Guard infantry sergeant serving in Afghanistan in 2010. About the same time a commercial firm, TYR Tactical, offered for sale (at $4,000 each) an almost identical item (MICO Machine Gunner's Assault Pack). The TYR pack used a longer sleeve (from the pack to the M240), which contained another 75 rounds (for a total ammo weight of 18.4 kg/40.5 pounds). The pack itself only weighs a few kilograms (under ten pounds).
Most infantrymen believe the Ironman or MICO pack would not be useful for all situations, especially during long patrols. The machine gunner carrying the pack and the machine-gun would also be wearing body armor and other essential combat gear. This would amount to over 50 kg (110 pounds). That can be handled for a few hours but not for long patrols over mountainous terrain. The ammo pack would be very useful for base defense or raids.
It's not unusual that the Natick and TYR assault pack designs appeared about the same time. The basic idea has been around for a long time and troops have put together improvised assault packs in the past. Many breakthrough ideas (calculus, radio, television, and numerous other bits of tech) were invented, independently, at about the same time by two or more people. Great minds think alike.
TYR produces gear for SOCOM (U.S. Special Operations Command) and SWAT teams, while Natick fields request from all army units and are increasingly getting innovative proposals from troops in the field.
