[SimonE]

Apologies for the thread necromancy, but I was trawling through some of the older threads and have some useful information to add.

These are the results from static tests of bomber defensive positions, from a test firing of 12 rounds at 600 yards. The dispersion is measured in feet and mils of arc (3600 mils in circle).

Boeing B-17:

Ball Turret: 15 ft/8.3 Mils
Sperry upper turret: 21 ft/11.7 Mils
Bendix chin turret: 23 ft/12.6 Mils
Waist K-6 mounts (closed windows): 26 ft/14.3 Mils
Side nose guns: 34 ft/18.7 Mils
Tail turret: 45 ft/25.0 Mils
Tail turret (early Stinger type): 61 ft/33.4 Mils

Consolidated B-24:

Ball turret: 15 ft/8.3 Mils
Martin upper turret: 20 ft/11.2 Mils
Emerson nose turret: 23 ft/12.9 Mils
Waist K-6 mounts (closed windows): 23 ft/12.9 Mils
Motor Products tail turret: 35 ft/19.3 Mils
Motor Products nose turret: 35 ft/19.3 Mils
Waist (open windows): 63 ft/35.6 Mils

Information is borrowed from one of the old Ubi-forum threads, but I believe it originally comes from a book in US turrets. I've seen the same figures reproduced on several different forums by several authors, so I'll assume its reliable until proven otherwise.