40MM Gun Firing (Sound only)
40MM Anti-Aircraft Gun Mount Mark 1 Twin OD 3782
40MM Anti-Aircraft Gun Mount Mark 2 Quad OD 4391
40MM Anti-Aircraft Gun Mount OP 820
40MM Machine Gun Mechanism, MARK 1, MARK 2, MARK 1, MOD 1, MARK 2, MOD 1
The power drives for the above gun mounts were designed and built by the york safe and lock co. These drives used a clutch mechanism which the salt water would get wet and the drive would then be jumpy, jerky and would slip and had to be constantly worked on.
The 40mm gun described in op 820 had hydraulic drives and was used to replace the york safe and lock drive on the above gun mounts.
In the first year of the war the 20MM Gun and the 1.1" gun shot down the most aircraft of any gun system in the fleet. The mark 14 gun sight was first adappted to the 20mm and 1.1" gun in about the mid point of 1942 as it became available. These were the primary air defense weapons systems at the time. The 1.1" gun quickly went out of service as 40MM Gun Mounts became available, the 20mm served by the thousands untill the end of the war and beyond.
The 40mm gun and the Mark 14 Gun Sight began to arrive in large numbers in the fleet by 1942 and this combination gun system gets the blue ribbon for shooting down the most aircraft during the war. 
