of fire of around 2.5 shots per minute. The shells were fired with a muzzle velocity of . As with other heavy German guns, these weapons used a fore propellant charge in a silk bag with a main charge in a brass case. These guns could hit targets out to a maximum distance of . The ships' secondary battery consisted of fourteen 15 cm (5.9 in) SK L/45 quick-firing guns mounted in armored casemates along the central superstructure. Each gun was supplied with 160 rounds, and had a maximum range of , though this was later extended to . The guns had a sustained rate of fire of 7 rounds per minute. The shells were 45.3 kg (99.8 lb), and were loaded with a 13.7 kg (31.2 lb) RPC/12 propellant charge in a brass cartridge. The guns fired at a muzzle velocity of 835 meters per second (2,740 ft/s). The guns were expected to fire around 1,400 shells before they needed to be replaced. The ships were also armed with eight 8.8 cm (3.45 in) L/45 Flak guns in single pedestal mounts. Four were arranged around the rear superfiring main battery turret and the other four around the forward conning tower. The Flak guns were emplaced in MPL C/13 mountings, which allowed depression to −10 degrees and elevation to 70 degrees. These guns fired 9 kg (19.8 lb) shells, and had an effective ceiling of at 70 degrees. As was standard for warships of the period, the s were equipped with submerged torpedo tubes. There were five tubes: one in the bow, and two on each flank of the ship. The torpedoes were the H8 type, which were long and carried a 210 kg (463 lb) Hexanite warhead. The torpedoes had a range of when set at a speed of ; at a reduced speed of , the range increased significantly to . Armor The Mackensen-class ships were protected with Krupp cemented steel armor, as was the standard for German warships of the period. Specific figures for the arrangement of the armor layout have not survived, but according to naval historian Erich Gröner "The outfit of Krupp armour was similar to that of the [preceding] Derfflinger class". The figures listed here are those for the Derfflinger class. They had an armor belt of thickness in the central citadel of the ship, where the most important parts of the vessel were