Medium Tank M7 at the US Army Ordnance Museum.
Originally a light tank design, the M7 grew until a redesignation to medium was necessary. The M7 used the same 75mm gun as the M4 Sherman, but its trailing idler suspension superficially resembled that of the M3 or M5 light tanks. The hull escape hatch can be seen between the front two suspension bogies, and a stowage box is mounted behind the turret on this example. (Photo by Richard S. Eshleman.)
The cast hull armor of the M7 was well rounded. (Picture from Development of Armored Vehicles, volume 1: Tanks.)
Details of the vertical volute spring suspension are visible in this closer shot. The drivers' vision slots are visible in front of their hatches, and the TC's and loader's split hatches are open on the turret roof. The aperture for the gunner's M5A1 telescopic sight is on the gun shield's left side, and the coaxial machine gun was placed on the right side of the main weapon.
Although appearing like other ball machine gun mounts, the D40771 used a gimbal-type suspension instead of a ball and socket joint. Aim was still by using tracers or impacts. (Picture from Weapon Mounts for Secondary Armament.)
Exploded and assembled views of the ball machine gun mount are offered on the left and right, respectively. Pins D and U in the exploded view were inserted into collar V, which provided pivots for the machine gun cradle C inside housing W. A spent case collection bag could be mounted on the rear studs, and an ammunition box holder was also provided. The machine gun was secured to the mount by its front mounting holes, while its rear mounting holes were used to attach the travel lock. An equilibrator spring was also used. (Picture from Weapon Mounts for Secondary Armament.)
