[magic452]

The ability of destroyers to evade torpedoes is a big flaw in the game.
They accelerate at aircraft speed.

To score hits on a DD in the stock game with auto targeting you must
1) DO NOT lock the scope on the target.
2) aim the first torpedo about a quarter of a boat length ahead of the bow. This will make the DD sit still.
3) shoot two more fish, 1 at the center or the stack and the second some where forward of that. Shoot these three quickly.
4) Best bet is to do this at night or in bad weather if possible This applies to any target

Make sure that you open the torpedo doors first. The "Q" key.

Most likely the reason the DD starts and than stops is she doesn't know where you are and your very lucky.

550 Yards is pretty close much closer and the torpedoes will not arm.

Good luck and good hunting.

Magic