Press 'x'

Also this might help, in general:

trainworld.us/nf-guides/

You better learn how to alternate those gun.
Better than failing and can't even land a nuke salvo, in which 96% of the time BB's player are.

ermm you can't fire both the guns in r slot and in t slots together

You cannot fire your R slot guns and T slot guns at the same time. Your R slot weapons are the main guns you should be using and usually the remaining T slot weapons are used for either torpedo launchers, depth charge launchers, or anti-aircraft guns. Pressing X only selects all weapons in the R slots, or all weapons in the T slots. pressing z/c allows you to change between your front and rear guns.

reason you have r slot guns and t slot guns is pretty simple... r slot guins are the ships main armament artillary!!

while the t slots are used for things like AA guns Torpedoes Hedge hoggs depth charges and stuff like that..

you will notice on your ship that your r slots have a significantly larger amount of space than your t slots do.. this basically means you cannot have the same guns in your t slots as you do in your r slots.

well you could but you have to have 2 pairs of gunners to work them.. however the r slot guns would be restricted to the t slot guns which would be utterly useless in a ca and upwards..

imagine having trip 15 inch guns in your r slots and only being able to fit duel 6 inch guns in your t slots..

those 15's are going to shoot much much further and have completely diffrent angles and velocity speeds compaired to the smaller 6 inch guns.

thats why you cannot fire all your guns at the same time.

t slots are for secondary armaments i.e. AA torps depth charges mines hedge hogs and so on.. r slots for primary artiallary.

if your still having trouble with this i insist that you google real life world war 2 warships and just take a look at them :)