Hi Andreas!
I'm the damage model guy of GWX. Will check the small merchants in the game to identify which one you ar referring to and will get back to you.
In generel,
Murphy's Law has great applications with a torpedo hit:
1) The randomised torpedo strength is always set at the lowest setting, while hitting the smallest ship
2) If the randomised torpedo strength is set at better than lowest setting, the torpedo hits on the wrong spot
3) If none of the above stand, then the ship never carries ammo, so it doesn't blow up
4) If all of the above stand, then the torpedo is a dud
5) If it is a dud, it is always the last torpedo you are carrying
6) Did I mention that while all of the above are happening, the weather does not permit you to use the DG?
Von