Board Thread:Fleet's Prepared-ness/@comment-31118942-20170730140825/@comment-26366865-20170730161309

Lightbaron has most of the important stuff covered, so I'll just add something here:

WashBoard17 wrote: In the situation that you wish to conserve screw usage the following are recommended; AP shell, T93 Sonar(possible to upgrade to T4) and 35.6cm gun.

You should only invest in upgrading the default 35.6cm if you plan on going all the way and turning it into a prototype gun. Even at MAX, the 35.6cm loses its value really fast (speaking from experience here), as getting better cannons gets progressively easier, and the cost of upgrading it to prototype isn't screw-efficient at all. You shouldn't be upgrading this unless you really have no other available options - which is not OP's case at all.