The MK6 depth charge projector was developed to widen the the area covered by the attack by increasing the number of depth charges that could be fired simultaneously. The use of rear drop racks was a useful strategy in WWI, but during WWII a submarine could evade this if it had already dived some time before. A more widespread pattern was needed to catch such a target. The obvious solution to this problem was throwing the depth charges far to the side, so as to create a sort of depth charge carpet.
During the latter part of WWI, the Y-gun was created for this purpose. This was a projector which fired two depth charges simultaneously off the port and starboard sides if the ship. These Y-guns were located on the centerline of a ship and having two barrels, forming a Y. A depth charge was set on each barrel to be fired off in support of the other charges several hundred feet outboard. While this was an effective addition to the anti-submarine warfare forces, its major drawback was that it had to be mounted on the centerline where little room is typically available.
A single barrel version of the Y-gun, the K-gun, was developed which could be mounted on either side of the main deck which fired one depth charge outboard. Four K-guns lined either side of the main decks of destroyer escorts.
The K-gun consists of a smooth-bore barrel attached to an expansion chamber fitted with a breech mechanism. The breech plug houses a firing mechanism that can be fired by local percussion by lanyard or electrical firing controlled from the bridge. Note the short stump to the right of the projector's main arm, into which the explosive charges were loaded.
The depth charge is launched attached to an arbor, with the action of the propellant against the base of the arbor. The arbor remains attached to cylindrical charges but is released from the teardrop models to take advantage of their streamlined shape and expended. Thus, an arbor is expended every time a depth charge is fired.
The projector is fixed and variations in range are obtained by varying the weight of the impulse charges. These are assembled in 3" cases using three standard weights of black powder charges resulting in ranges of 60, 90 and 150 yards.
Watch the k-gun in action aboard the USS PARLE DE708!