We are taught from our very first minutes in SH3 that the best AOB is 90 degrees. But it's not quite true when using magnetic pistols. When target is a small ship, the torpedo will travel too much under her keel before it arms and detonates, thus dealing less or even no damage. So when you use magnetic, the more acute AOB could be a better choice.
Impact is not always an option, especially with battleships (because of their belt armour under the water line) or with ships of shallow keel. So my advice would be to train using magnetic triggers, as it would be a real shame to have a BB in the scope and not to sink it.
