Here's another way to intercept a contact. Practice in a single mission tho so you get used to doing it this way.... but only if you want to. Works great even tho it is a bit of a cheat.
Scroll in so you are closer on the nav map and have one way point ahead of you that's still on the screen. Raise TC to no more than 32. With TC at 32, or lower [lower is good the closer you get], click on and hold the waypoint so you can move it with your mouse. You'll see the direction the contact is moving, so just move your waypoint around so you have an intercept. When the contact pops up as a ship you're all set. You can adjust and/or extend your sub's course accordingly for using the deckgun or a torpedo shot.
Edit: photos and more added.
Here's what I do for a target:
Click on Turn TDC ON.
Use your mouse to Lock, and again to Break Lock. You should now see the box to Turn TDC On. Never mind will be at the bottom and will shut off TDC. So be careful you don't shut it down.
Click Turn TDC On and Lock again. Now you'll see the Recognition Manual. Identify the ship and get the info you need. I get the ships draft to set my torpedo depth. Now Break Lock. Now look in the box and it will say Turn TDC OFF. Click on it to turn it off. Now all you have to do is line up where you want to hit the target. OFF is is a must. You want to see Turn TDC ON so your torpedo will go straight and true to the target. I usually use Shift/Space to fire off a torpedo. It's faster than using the mouse to click on Fire.
Works 99.9% of the time. Escorts can be a bugger as they'll speed up and/or slow down, turn, or even stop. Let them get close, within 700 meters or less, and fire a steam powered torp set to FAST. They can't do a thing but blow up.
Practice this in a Single Mission so you get the hang of it, then...... Sink em all.
Good luck.
