Torp Arming?
 

I know i read somewhere that it takes 300 m for a torp to arm...is that accurate and if so can i somehow reduce that distance by...doing something(idk)? I'm in a really good position to sink a large merchant(at 200 m) but everytime I fire it refuses to detonate(on magnetic) even when passing just under the keel.

Yes the torpedo needs at least IIRC 250m to arm but 300m is a save number. SO don't fire within that 300m mark.

But remember the torpedo has to be in the water for 300m so if the ship is moving away you can shoot closer.

The lowest is about 320m I found to get a hit at close range.

Magnetic seems to arm a little closer (250 meters) than contacts (300 meters). If the ship is traveling away from you, you can fire closer, but consider the 300 meter mark to be as close as you want to get!

Give it a magnetic as the ship moves away! ;)

If aiming from her stern that is!

I find that not range but time of travel is the determining factor. I.e: shooting at 250 meters with a fish set at "fast" will give you a dud, but with speed at "slow" will not.

I don't know if this is historically accurate or not.

Nope, the game treats every torpedo the same, they arm after a certain distance (250 or 300m), independent of speed.

Rule of thumb (magnetic and impact) 300m.

Falke 400m.

If traveling faster distance might be less than going slow, if the target is moving away, that's why it differs from slow to fast torps.

There is a small impeller at the nose of the torp which 'arms' the torp after a specific number of turns; it withdraws a safety device. Therefore it seems reasonable that the speed of the torp affects the rate at which the arming takes place, the slower the torp the longer to do the required number of turns (with an allowance for impeller efficiency).

i try not to fire any closer then 350-400 metres just to be extra safe with the arming, however i have managed to get a hit at 254 metres.