The guns used three different charges, depending on the situation: a full charge, a full flashless charge, and a reduced charge. The standard full charge weighed 15.2–15.5 lb (6.9–7.0 kg), the flashless charge was slightly heavier at 16 lb (7.3 kg), and the reduced charge was significantly smaller, at 3.6 lb (1.6 kg). Both full charges provided a muzzle velocity of 2,600 ft/s (790 m/s) in new guns, but as continued fire wore down the barrels, muzzle velocity degraded slightly, to 2,500 ft/s (760 m/s). The reduced charge's muzzle velocity was correspondingly lower, at 1,200 ft/s (370 m/s). Each gun was supplied with 450 rounds, and was expected to fire 4,600 shells before it was worn enough to warrant replacement. At the maximum effective elevation to engage surface targets, 45 degrees, the guns could hit targets up to 17,392 yards (15,903 m) away. The maximum height at which aircraft could be engaged was 37,200 feet (11,900 m).