Although the U.S. Air Force is replacing the 40mm cannon in its AC-130 gunships with 30mm autocannon and missiles, it was faced with the prospect of these M2A1 40mm weapons being retired earlier because the supply of spare parts had been exhausted. Then, a U.S. Army officer who had been a liaison officer to the Greek Army let the U.S. Air Force know that the Greeks had recently (2005) retired their half century old M2A1 anti-aircraft cannon and still held a supply of spare parts. These actually belonged to the U.S., as the M2A1s and the spares were given to the Greeks in the 1950s as foreign aid. An air force officer was sent to Greece, found and inspected the spares, and made arrangements to ship them back to the United States. All this cost less than $15,000. The parts consisted of 139 barrels, five breech rings, and several other spares that would cost, if manufactured today, over $14 million. This was sufficient to keep the air force M2A1s working until they reached the scheduled retirement over the next decade.
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.