Boeing has begun test-firing its new 12.7mm Bushmaster chain gun. Basically a scaled-down copy of the Mark-44 Bushmaster (a 30/40mm weapon), this is intended to provide a replacement for the tens of thousands of M2 Browning 12.7mm machineguns in service around the world. While the M2 is one of the most common heavy machineguns, it has several drawbacks. It has only single-shot and continuous fire modes, only one ammunition feed, cannot use all of the available 12.7mm ammunition types, and wears out after 30,000 rounds. The M2 produces toxic gas from its chamber, a problem in confined turrets. The new 12.7mm Bushmaster has many advantages. It is externally powered (24volts), so a mis-fired round will not stop it from cycling. It has a burst limit that can be set at 1, 5, 10, or 20 rounds. It has two feeds, allowing the gunner to load two types of ammunition and select which one he wants for each burst. The weapon weighs 65 pounds and is designed to allow use in remotely-operated external mounts--Stephen V Cole