In the in-game experience, i've noticed that you can fire all your torps at praticaly the same time, and they will all explode upon contact (providing none are duds), even if they are shot, say, a fraction of a second from each other.
My point is: in real life, the detonation of the first torpedo could or could not induce a premature detonation on the second torpedo coming just behind it? Or damage its firing pistol, or wrecking it complete, or etc etc etc? My point is, torpedos were so delicate, that I often wonder if a skipper would wait a few seconds between torpedoes shots, just to avoid the first detonation causing any damage to the other torp following just behind.
What do you history buffs have to say about it?