Eh, we can go like this forever... I will make one more attempt to explain.
Those guns are on the hull of the ship, maybe in some rums on the ship and spare compartments. But under no circumstances can you mix ''Cargo space'' with those spare compartments and small empty places on the ship. ''Cargo space'' is the place where you store your commodities for transporting not the place where you will place your guns with which you want to shoot.
Now to test your logic:
You want to put guns in cargo space, tell me how will you shoot with them from inside of the ship? Will you make a big hole in the ships armor and destroy your own ship in process of shooting enemy ship?