[tedhealy]

http://www.americanheritage.com/arti...998_4_56.shtml

Further testing revealed the trouble: The spring-driven firing pin, which moved at right angles to the axis of the torpedo, was being squeezed by the compression of other parts of the warhead and couldn’t overcome the friction caused by a solid, head-on hit. Within days several solutions were found. The simplest was to pare down the weight of the pin to reduce the friction on its guide studs. The Navy lost no time in putting this finding into practice, and on September 30, 1943, the Barb left Pearl Harbor carrying 20 torpedoes, the first ones to have modified firing pins in their Mark 6 exploders.