The guns fired at a rate of 1.5–2 rounds per minute. The Mk V "Heavy" gun fired a variety of shells, including high explosive and armour-piercing rounds; they all weighed 1,400 lb (635 kg). The guns were loaded with MD45 propellant charges that weighed 297 lb (135 kg); these were stored in silk bags. This provided a muzzle velocity of 2,491 ft/s (759 meters per second). At maximum elevation of 20°, the guns had a range of 23,740 yards (21,710 m), though at the maximum effective elevation of 15°, the range was somewhat shorter, at approximately 20,000 yd (18,290 m). At a range of 10,000 yd (9,144 m), the gun could penetrate up to 12.5 in (318 mm) of Krupp cemented steel armour, the type used on contemporary German dreadnoughts.