In regards to the plans for increasing the range of guns/turrets available. Could you use a slider based system where people can set the design specs. eg. 12" shell, 55" barrel length, 3 barrels per turret.
And then use a linear graph to guesstimate the stats based on known stats of real guns.
I'm a first year Comp Sci student and very interested in topics like this so I'd love to dicuss it more.