ABSTRACT
At the start of the Run to the South, firing began when the range between the opposing battlecruisers was 16,000 yards (about eight sea-miles or nine landmiles). At that distance, the waterline of an enemy ship was pretty well on the distant horizon,2 while even a battlecruiser almost 700 feet long could be entirely obscured behind a little finger held vertically at arm’s length. It was no easy matter to hit such an apparently tiny target from a ship that, except in a flat calm, would be rolling, yawing and pitching, and when both ships were steaming on different courses at speeds that might exceed 25 knots. This chapter describes the essential principles of long-range shooting at sea, and a few key instruments that embody those principles. It also introduces those unavoidable ‘terms-of-art’ (in italics on their first appearance) which are indispensable in describing the technical evolution of the rival systems of fire control. Especially at long range, hits cannot be made simply by pointing the gun along the line-of-sight to the target. First, as soon as a shell leaves the barrel, it is pulled downwards by the force of gravity. Thus the barrel must be elevated i.e. inclined upwards from the line-of-sight; the shell then follows a curved trajectory that should end on the enemy ship. However, the elevation can be set correctly only if the distance or range of the enemy is known. Second, when viewed from above, the shell does not fly straight. Due to the stabilising spin imparted to the shell by the barrel’s rifling, it drifts sideways (to the right with British guns), by several hundred yards at long range. Thus, to correct for drift, it is necessary to apply a suitable deflection i.e. to ‘aim off’ horizontally from the line-of-sight.
