3.9" are good as a HA gun and AA gun. With the intoduction of Tsukikei there is finally
good ship for that. You can put L for range or D for reload and have fun. Dmg for HA is
worst than others nations guns but often enemy running away after few HA salvos. You need
to practice HA ability. Do not use HA guns in DD rooms. Targets are often too fast. Best
way is to load some HE shells along with AA and join all welcome. With good gunners
shoting aircrafts is easy and HE shells will be useful for self defence. Best way to
practice HA is mission whoring (D version and 500 shells, enough to sunk all 4 battleships
without any damage to your DD - try to keep BBs between 65-70 degrees) or Op. Convoy. HA
is a good way to get extra experts.

oi oi oi

yeah thats right AA in higher lv can reaload like crazy.....coz im using my cv and aa
always shoot continuously until my plane s down....T_T

I have heard of people at higher levels using these guns with an unbeleivable reload, shredding ships to pieces. I personally like the 5.5, my reload is to slow for the 5.5

Interesting! Thanks for the quick reply!
I am using a Fubuki wit 3 4*Torplaunchers and 3 2*5.5 Guns and i am quite satisfied with that setup. It is a shame that those big guns fit on DD's at all! If not all others would use unrealistic guns on their DD's i would take the 3.9" so i could double as AA Ship.

most ppl would prefer to stay at dual 5" than the 3.9". usually y is the dmg output cause the 3.9" doesnt light enuf candle to match against the 5" and for range resons as its too much work utilizing its potential for high angle atks. lets just say the 5" is just more easier to use for noobs than what most ppl would think.

obviously the more gun slots the better so i mostly think the tsukikei but then theres the fubu for auxillary uses but then again, everyone would rather be a TW for weight reasons as it has limited space(weight) for guns and it gives less xp for sailors in a specified skill if you use both guns and torps. non-historically but in game, the dual 3" and dual 4.7" is most widely used for AA in japs especially for kuma.