The M2A1 is based on the Swedish World War II Borfors design. Each M2A1 weighs a ton and has a 2.34 meter (7.25 foot) long barrel and fires 40mm rounds at 903 meters (2,800 feet) per second. Max range is 7,000 meters. On the AC-130 rounds are fired one at a time, but the M2A1 can fire 240 rounds a minute in automatic mode. The automatic loader holds seven rounds. Each high-explosive 40mm round weighs 2.15 kg (4.75 pounds) and includes a 900 gram (two pound) projectile.