yea - in 39/40, I tend to stay with impact.
BUT
With the TW damage model, one-sided hits are a lot less effective than two-sided hits in reducing buoyancy - i think that a keelshot breaks compartments on both sides of the keel - double damage essentially. With impact shots, I find you can blow compartments all along one side of a ship without sinking it - it just gets a wicked list.
So - Mags are the best, but the riskiest. I never use them in anything but calm weather - a premature det isn't just a dud - it screws up all the other shots that were fired with it.
Also - I've found that you have to get the depth right - you want the mag to go like 0.5m under the keel - no more. I've seen a few sail under without going off.
So - with a big ship, you want to break as many compartments as possible, so go with a mag (weather permitting). Start with a T2 mag under the keel ( i usually go for bow because a heavy bow can basically stop the ship) and follow if necessary, with fast T1s set to impact all along the side. That should do her.
Kb
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