No, because it requieres Huge gunner to use it.

so you can use level 74 gunner or armament sailor not classed to heavy gunner or
such for ss4 guns ?

Thank's for clearing that up everyone. And by the way, my km sub crew is only lvl31.

All you need to use the 20mm quad AA is 2 main gunners lvl 74.
There is no machine gunners in KM, even if you are assuming something which is wrong.

If you hover your mouse over the KM SS deck gun it will, in bold, display the "skill"
which is required to use the gun.

If you look at your sailors you can see, again in bold, the particular skills those
sailors possess and from that put the appropriate sailor on the deck of your sub.

But to make it easy for you place a normal gunner on the deck slots of the guns and away
you go.