Just How accurate are They?   (http://www.fas.org/man/dod-101/sys/ship/weaps/mk-7.htm) And Just How did They Figure That Out? The distance traveled by a projectile is found by using R=(Vi)sin(2a)/g Where: R= Range Vi=Muzzle Velocity g=The Force of Gravity a=Angle of the Barre to the Horizontal   The Time that it takes the projectile to reach the target is found by t = Visin2a/g Where: t = Time to Target Vi= Muzzle Velocity a= Angle of Barrel to Horizontal g = Force of Gravity This is a shadowgraph of .308 winchester,(which has the same shape of a 16 inch shell.) (http://www.nennstiel-ruprecht.de/bullfly/fig2.htm)   Since the Muzzle Velocity (2,300)and the force of gravity(9.8m/S2)are constant the only thing to do is angle the barrel to fire the projectile the wanted distance.     There are a few other forces that can be taken into account in the firing of a projectile, such as the centrifugal force , the coreolis force and the Magnus force but these forces are very small and comparably insignificant to put here.