1) In primary mode the Stingray is a kinetic weapon that is somewhat useless when used against ships, since it has a huge spread and a short range and its effectivity suffers from the slow speed of the projectiles. It IS though my weapon of choice when it comes to destroying tanks and other ground targets like turrets or generators, because of the secondary firing mode.

The secondary mode is meant to fight against ground targets - the Stingray fires a salvo of shells towards your target that covers a relatively huge area around the target, creates a fire in this area and is able to destroy even stronger tanks in one or two shots. It is almost impossible to use the secondary mode against swimming targets, although it can be used to shell the hell out of slow and big targets when you can get above and relatively close to the enemy. But then again, there are better choices for this so the Stingray is mainly used to fight ground based tanks.


2) As far as I understood how the weapon works the secondary mode does exactly the same amount of damage per projectile as the primary mode does. The only difference is that it drastically reduces spread and fires "to the point" at the cost of a much slower firing rate and, if I remember correctly, a somewhat higher energy consumption.