[TwistedFemur]

When they tested the MK14 during trials it had a 70% failure rate

Tests were carried out by COMSUBPAC's gunnery and torpedo officer, Art Taylor (ex-Haddock). Taylor, Swede Momsen, and others fired warshots from Muskallunge[37] into the cliffs of Kahoolawe, beginning 31 August. Their third test shot was a dud.[38] This revealed the firing pin had not been able to contact the detonator hard enough to fire the warhead.[38]
To avoid "shaking hands with St. Peter" (as Lockwood put it),[38] E.A. Johnson, USNR, supervised by Taylor, dropped dummy warheads filled with sand from a cherry picker from 90 feet (27 m). In 7 out of 10 of these trials, firing mechanisms bent, jammed, and failed with the high inertia of a straight-on hit (the prewar ideal).[39] A quick fix was to encourage "glancing" shots[40] (which cut the number of duds in half),[39] until a permanent solution could be found

http://en.wikipedia.org/wiki/Mark_14_torpedo