Early British experiments paired gun-cotton charges with lanyards, but tangles and unreliable triggering encouraged chemical and then hydrostatic pistols. Jellicoe's request to adapt a naval mine produced a very large weapon, while HMS Vernon developed the more practical Type D and a smaller charge for ships too slow to clear the blast. HMS Farnborough, a Q-ship, achieved the first successful depth-charge sinking against U-68 off Kerry Island on 22 March 1916, although only two more submarines fell to depth charges that year. Scarce production initially left anti-submarine vessels with only two charges, and wartime experience drove loads sharply upward. Extra charges and racks added dangerous topweight, forcing ships to remove other weapons or find weight savings. Because ASDIC contact disappeared as an escort passed over its target, stern racks alone could leave too narrow a pattern against a last-minute submarine maneuver. Peripheral K-guns, paired with stern racks, spread six to ten charges across the probable target area while preserving valuable centerline deck space.
Notable Point · 1:19:52-1:28:50
From lanyard charges to K-gun attack patterns
Depth-charge development required reliable triggers, adequate ammunition supplies, and attack patterns wide enough to catch a manoeuvring submarine.