Just FYI, though, defensive guns are extremely counter-productive. For the weight of one man in full kit, the gun, ammunition, those same bombers could have flown higher, faster, further with more bombs. Not one defensive gun deterred a fighter from attacking a bomber--hence why unescorted bombers were so vulnerable.
Just for an idea: a B-25 Mitchell has a crew of six (pilot, copilot, navigator/bombadier, turret gunner/engineer, radio operator/waist gunner, tail gunner). It carried 12-18 .50cals, and 6k pounds disposable stores. Assuming each airman weighs about 225 (fully kitted out) and rounding to 90 pounds for each .50, that's about 2430lbs. Dropping the defensive weapons and realigning the engineer to also do radio, that's an extra ~1500lbs of bombs over the target