No map contact updates tips

[black1]

Ok all i want to start playing with no map contacts and i was wondering some of your best tips to intercept a contact. I get a report saying a contact bearing say 320 degrees long range, i immediately mark a spot 320 degrees how far out from my sub? and start the stopwatch and go for 3min 15 secs and mark another spot at contact now 351 degrees how far out from my sub? im thinking it does not matter how far out, am i correct for now. I then check the heading of the sub and get a speed calculation by those 2 marks correct by drawing a line from 1st mark to the other mark. Then set an interception point based on those readings. How far out is "Long Range Sir" . I dont really want to ping him to find distance because it could be a warship or destroyer correct. Could some of you fine chaps explain some tacticts to use when playing with no map contact updates, maybe by screenshots or video would be great, thanks all for the tips and being so helpful here.