|Type||500lb GP Bomb|
|Country of Origin||USA|
|Explosive Charge||267lbs TNT or Amatol|
|Minium Safe Altitude||2500 ft|
|AH Damage Value||586lbs|
|Type of Target||Steel Railway bridges|
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The American version of the 500 lb general purpose bomb was the AN-M64. It's explosive charge consisted of either 267 lbs of TNT, 262 lbs of Amatol, or 274 lbs of Composition B. The AN-M64 was painted olive drab with a 1" yellow stripe marking the center of gravity, with a stripe around the nose and rear of the bomb. It was 57" long and 14" in diameter with a 0.3" thick steel casing.
The British defined a general purpose bomb with a lower charge/weight ratio (roughly in the 27%-35% range). The 500 lb GP MK-I through MK-VI had an explosive charge of either TNT or Amatol weighing in the neighborhood of 145 lbs. Their total lengths ranged from 68-3/4" to 70-5/8" with a diameter of 13" and a casing thickness of 0.72"-0.875". The British equivelent of the AN-M64 would be the 500 lb MC MK-III which had a charge to weight ratio of around 50%. The British dropped 1,729,611 GP and MC bombs from 1940-1945. 
True to its US designation of "general purpose", the 50% charge/weight ratio 500 lb bomb was employed against a wide range of targets, including railways, light naval vessels, and a plethora of types of "soft" structures. It was deployed from both heavy bombing platforms, and from tactical aircraft. The minium safe drop altitude listed for the AN-M64 was 2500 feet. USAAF documentation listed target examples of: "Steel railroad bridges, subways, concrete docks, light cruisers"