- torpedo differences
G7A - steam powered, higher speed up to 44knots with 3 speed choices availiable but leaves a visible wake on the surface when fired. more reliable at the start of the war than the G7E electric.
G7E - electric limited to one speed of 30 knots. no wake when fired. more chance of duds early in the war though fixed by the time the Axis take Norway. Advantages are obviously for daytime attacks staying undetected and especially for shooting at warships whose ability to accelerate makes them harder to hit with the torpedoes they can spot.
- impact or magnetic
not better or worse imo, just different. impact you are trying to hit the hull below the waterline, magnetic you are trying to have the torpedo pass under the hull by around 1-2m.
- 1 shot kills
various ships have different weak points which you will come to learn ie ammo bunkers, fuel tanks where a single torpedo will do lots of damage. personally i've found the best chance for a 1 shot kill is the magnetic torpedo under the hull that breaks the spine of the ship.
- torps not working
could be a) a dud , or b) the impact angle can affect the torpedo detonator. The further off 90degrees AOB your shot is the less likely it is that an impact torpedo will work, magnetic torps should not be affected by AOB (** i think**). Just think of it as a glancing hit of the hull that wasn't enough to trigger the detonator to register an impact.
- detection range
varies by year and quality of crew on the DD. lots of posts on the mod forum about detection distances etc. crew quality is random from green to elite and different ships at different time points have different equipment so it is hard to say. early in the war they have a hard time finding you at all, later in the war you will feel that you have a giant striped bouy attached to your conning tower with a big I AM HIDING HERE flag on it.
- range
min distance to arm the torpedo is 300m , max range goes out to about 7.5km with a g7a on slow speed but the reality is that the further away you are the greater the margin for error and the more chance the target has to change course and or speed. rule of thumb to get closer than 1000m though I try to get closer again if possible.