I did a really successful sonar only attack once. Hit five of six torpedoes.......on the USS Essex.
It was not my finest hour.
WernerSobe's sonar only technique in the Sub Skipper's Bag of Tricks thread works masterfully, as it would have in real life. I have a sonar only Dick O'Kane technique in that thread also, which is a bit more relaxed in execution but maybe a bit more deadly.
All the sonar only techniques work better in the game than they would in real life because we know that the return sound from the target is an exact (I think it's four degrees) number of degrees wide, where in real life that would vary with conditions. That would result in a bit more bearing error than we have. It still would have worked in real life.
The problem was that early skippers learned that the dangers of exposing a periscope were vastly overrated if your were reasonably cautious. And there is no doubt that you feel more secure and target much more accurately if you use the periscope. That left them with no reason to use sonar targeting.