I'd say, very soon - IIRC one of my KM BOs started seeing shells in the late 70s, unboosted with 100 vets and lots of experts - at around 1200 displayed ability (but possibly for slightly longer ranging KM guns).

Last time I check there is no BB3 at lv 74 the lowest is RM lv 76.

U will spot ur shells at BB3 lv(76-79), at BB2 is very common if player can't spot their shells using LHE... unless they are using elite boosted potential BO.

With Elite Pot, boost and 100 vets you can already start taking of rookies on BB1 level.

My US BO (120) has only 200 experts and 140 vets which makes him ultra light. IT's not like it's a huge advantage since it only gives you an extra 2 bulge.

But as for your question - (if you don't want to spend money) - use an AA ship and keep burning experts until you reach (AT LEAST) 100 vets, then fill up you experts to the max amount of sailors for you BO. Keep checking your guidelines from time to time to make sure they don't become too long.

Oh.. and make sure it's boosted or you will be shooting blind until you reach BB4 (I had this problem myself), unless you have like 200 vets or something like that.