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The B-17C model did not have gun turrets; the lower and upper defensive positions were a bath-tub like enclosure for the prone belly-gunner's position, and an overhead dual .50 ring mount. The mounting adapters and ammo cans were manufactured by the Edgewater Steel Company.

There are good views of this early equipment in the motion picture Air Force, produced during 1942 and released early in 1943 (available on DVD, Warners). The actual gunnery sequences are simulated; the M2's seen are simfire replicas, perhaps the first ever M2 replicas and the first simfire guns. The actual M2 cannot be actuated by blankfire; the M2HB used by land forces has a large, complex muzzle attachment to make blank fire possible for military exercises.

Here is a view of an un-mounted can:



In this scene a tail-gun position is being improvised and Sgt. Winocki (John Garfield) has asked for an "ammo can;" note the flat hooks on the lower front by which the can is clipped onto the E-12 adapter's sidebars. This puts the can up high, and necessitates a feed-chute which gives the can its distinctive shape. Here is the probable raison d'etre for this high-slung can, the belly-gunner's position. Note the low ground clearance here, which makes a conventional low-slung can impractical:



This position was made obsolete by the introduction of the Sperry Ball Turret, which also made the special-shaped can unnecessary; it is my understanding that they were replaced in initial wartime production, for the waist-guns (which had also used the special can), by standard-style low-slung deep-drawn boxes with open tops. The individual 100-round cans in turn became obsolete with the introduction of 600-round feed chests, with flex-tubes and electrical-feed assist devices connected to the M2's.

Here is another Edgewater adapter that went obsolete with the introduction of the top turret; the overhead twin .50 caliber ring mount:



Note the curved, double-capacity Edgewater cans, which are more securely latched to this mount which swings through 360 degrees, firing through the overhead. You can see the disadvantage of these early gun positions; limited field of view, limited field of fire.

IIRC, most of the B-17C's were upgraded by the addition of turrets, and I would surmise that these overhead mounts probably became so much scrap metal in the process. The E-12 mount survived long enough to make it into the government documentation, which was not published until 1944:



Here is a frontal view of the E-10 ring-spring recoil adapter:



Here is an alternate construction on the E-12 adapter; the main difference seems to be the construction of the sidebars with separate trunnions:



I have made inquiries to the U.S. National Air & Space Museum regarding the B-17C belly-gunner's ammo can, seeking any mil marks or other info, but have not yet heard back from them.

Regards, John

Correction; the Ammo box was designed by Boeing, the P/N being 15-7469. This information comes from the Smithsonian National Air and Space Museum, archives division, from whom I just today received a response from my letter of 14 July 2012! Here is a photo I just took of my 1:2-1/8 scale "Boeing side-gun ammo box":



These came with the aircraft from the factory, hence they have no Army P/N, and are, therefore, not listed in the B-17D Parts Catalog. Use of these individual ammo boxes was discontinued sometime in the second half of 1943, probably after July 22. Individual ammo boxes were supplanted by bulk feed with flexible feed tubes, increasing individual gun capacity to 600 rounds or more, depending on the size of the bulk-feed chest in use.

Regards, John