I think most of you are forgetting something... convergence. In a fighter, no one gun, or combination of guns, (except cowl-mounted) is shooting straight ahead. The wing guns are all shooting at a slight angle, the bullet paths converging into one group at the distance set by the pilot in the hangar. Nearer or farther than this distance, and the fighter's bullet paths are not concentrated in one small, devastating group, but are instead spread out over a wider area. In the bombers on the other hand, the gun being used to sight with is shooting dead on straight, is sitting in a nice, smooth riding turret, and has potentially several other sets of guns firing also. The primary gun used maintains a farther "virtual" effective range, because of the straight path of the rounds. The other guns that are "auto" firing must rely on convergence, but when you can fire dead on from 1.3k or so with the primary gun, the slight inaccuracy of the secondary guns is not a problem. In fact, they help to compensate for any mis-aim by the gunner on the primary gunsight. In essence, there are two distinct bullet paths being fired.. one straight down the middle, with obvious longer accuracy range, and the secondary path(s) that cross over and cause a spread pattern similar to that of the fighters. Sorta like firing a shotgun and a rifle at the same target, at the same time, from the same spot. Only makes sense that any relatively steady target is dead meat.. or rather minced meat.
