There have been a good number of submarines that are at the bottom of the ocean due to their own torpedoes. USS Tang (not in the tube, but it circled around and destroyed the launching submarine), USS Scorpion (I think it was a hot run torpedo), The Russian sub Kursk. I'm sure there are more, but that's what I can think of off the top of my head.
Regarding the USS Tang, there's a GREAT book about that submarine.
