A second decision regarding the armament was also to be made. The first Lord of the Admiralty, Winston Churchill, strongly advocated for the new untested 15inch guns for the ships main armament. These guns were developed in secret as a 14inch test gun. They were finally installed and soon after launch were proven a great success at the Battle of Jutland where the ships gunnery capabilities were specifically mentioned in battle report of the German Battlecruiser commander - Vizeadmiral Franz Hipper.
The ships were designed to a displacement of 31.500 tons but at the very beginning this number proved to be too low. At launch Warspite weighted 33.140 tons - a number that continued to rise throughout its entire career although 1400 tons was saved from new machinery in the 1934 refit. The weight issue meant that the intended 25 knots was never reached.
The design speed was 23 knots at 56.000 shaft horse power. At trials in 1915 the ship ran 24.1 knots at 56,600 hp. At an overload of 75,500 hp it managed to go 24.65 knots - just above half a knot for 20,000 hp....quite modest. In the 1934 refit programme new machinery was installed which gave 80.000 hp and the oil consumption was reduced by 30%. Furthermore a considerable space and weight reduction was achieved.
The ships were equipped with 4 three bladed shafts. They had a diameter just above 11ft and operated at a maximum of 275 rpm. Two rudders were placed to give the manoeuvrability required for naval operations. The placement between the shafts instead of behind them gave them poor manoeuvrability at low speed but good at high - which of course is beneficial for a ship of war.