Hi,
there is a very complete guidelines-list in the IJN forum (made by gghalley if I remember correctly) that gives you some basic antisub knowledge and techniques.

One thing you should always have in mind is that your US subs have a very high rate of duds, so staying at max range (either of the long-range torps or the short-range torps) help to counter that disadvantage.

Other thing to take into consideration is the number of torps KM vs US: ss4 vs ss4, you have 1 more rear torp (4-1 vs 4-2); ss5 vs ss5, its 4-2 vs 6-4; ss5.5 vs ss5.5, it is 6-0 vs 6-4 (if i remember correctly, the Balao fires 6-4, haven't use it in a while). So gradual shooting, proper "armor" (belt+bulge) and knowing when it is worth it to crit and when to stay, take the hit and have a better shooting position, are good ways to counter a KM sub.

Other than these , I recommend you again to read gghalley remarks about how to engage in a sub battle. It is truth they were made for IJN, but some principles in sub-fight can be used mutatis mutandis for all other nations.

Hopefully this will help you.

Best regards,

Ade 

Yes there is a very complete guide about this so I would not reiterate. But if in doubt, observe how other SS players fight their KM enemies in battles. I know it's hard, but it's also fun

the way to fight anny ss it to get on it back side 

aspecial the km ss

the km ss have a low number of rear torpedostubes compaidt to outher nations and  km torps haveaboud mid lvl damage

most ss players have more torpedos loaded in the front tubes then they have in the rear

this has to do with the low exp subplayers get and there for have to go after the big targets to get some exp

and those big targets if used correct are able to out run subs

u wont have time to fire your fronts at a bb and turn around to shoot the rears befor u compleet your turn the bb wil have moved out of range  

so for bb hunting u use the fronts and chase the target

but this leves u in a disadvantice vs ss cos in an ss vs ss u will need your rear torps to help u out

it all comes down to if u want to hunt subs in your sub of kill the bb/cv and you ballace your torpload on wat u want to do 

the best tactic for fighting KM subs is......

get said KM sub to chase you back toward your own side.

stay far enough away that you are out of range of his torps, but just slightly.

the ships on your team will gladly assist you with PHH, by shooting "towards" the enemy KM sub. this will not allow the enemy KM sub to get any damge on you or sink you. you will be sunk by your own team not the KM sub.

VICTORY!