A few issues to work out...
I had a problem with more than one gun being in "manual" mode, and therefore controlled by the mouse. I was trying to control one of the initial cannons and the EMP shell cannon at the same time. The regular cannon shot ust fine, in the direction I had the mouse, and its usual shell. However, the EMP was firing THE SAME round as the regular cannon and at some odd angle that seemed like about half of whatever the first gun was aimed to. As soon as I switched the EMP to "automatic", it began firing what I assume was it's intended round... a white ball. Switch it back to manual with the other cannon still on manual, and it went hay-wire again. Seems like some edge-cases need ironed out within the code.