[Crannogman]

Manning the gun yourself, you have the advantage at long ranges. I cannot recall the last time I was hit by something I was shooting at before I sank it - but I usually use deck gun at night, and start at about 8000y. The only daylight fight I can think of was against a lone 1500t patrol boat east of the Marshalls where he could not call for reinforcements and I could get home soon.

Have your sonarman ping them frequently (before almost every shot) to range-in quickly. Observe the fall of your shots - if you are moving East and the target is to the North, your shells will fall East of your aiming point. Waterline shots are great unless the target is coming straight at you - aim for their guns & superstructure instead to set them afire.

At best you can bring 2 guns to bear (but your AI guncrew is generally useless), while enemy combatants will have at least 2. Take them out before they can find your range. If there are multiple combatants/escorts, lure them away and sink them one by one. Expect to use 30-50 4" shells per combatant.

The deadliest merchant I have encountered is the 5100t medium European composite Zinbu Maru - it usually requires multiple torpedoes and has a good aft-mounted deck gun. I usually use the deck gun to finish-off wounded merchies - they usually turn away and may zig-zag, but are easy to put down. The Zinbu is usually harder because it will shoot at you as it scoots away, plus it is a relatively small target with low freeboard and shallow draft.

PS - you'll need to turn up the Gamma for good shooting at night. This may, to some, be construed as an ahistorical, perhaps unrealistic, hack. Since the game does not reward you for heavily damaging an enemy ship, I consider it fair to deliver a 4" [I]coup de grace[I/] even under unrealistic conditions