were removed in 1917. A pair of QF six-pounder () Hotchkiss anti-aircraft guns on high-angle mountings were mounted on the quarterdeck in 1915. They had a maximum depression of −8° and a maximum elevation of +60°. The shell was fired at a muzzle velocity of . They were replaced by a pair of QF 3-inch 20 cwt guns on high-angle Mark II mounts in 1916. These guns had a maximum depression of 10° and a maximum elevation of 90°. They fired a 12.5-pound shell at a muzzle velocity of at a rate of 29 rounds per minute. They had a maximum effective ceiling of . Dreadnought carried five 18-inch (450 mm) submerged torpedo tubes, two on each broadside and one in the stern. Twenty-three torpedoes were carried for them. In addition six torpedoes were carried for her steam picket boats. Fire control Dreadnought was one of the first vessels of the Royal Navy to be fitted with instruments for electrically transmitting range, order and deflection information to the turrets. The control positions for the main armament were located in the spotting top at the head of the foremast and on a platform on the roof of the signal tower. Data from a Barr and Stroud FQ-2 rangefinder located at each control position was input into a Dumaresq mechanical computer and electrically transmitted to Vickers range clocks located in the Transmitting Station located beneath each position on the main deck, where it was converted into range and deflection data for use by the guns. Voice pipes were retained for use between the Transmitting Station and the control positions. The target's data was also graphically recorded on a plotting table to assist the gunnery officer in predicting the movement of the target. The turrets, Transmitting Stations, and control positions could be connected in almost any combination. Firing trials against in 1907 revealed this system's vulnerability to gunfire, as its spotting top was hit twice and a large splinter severed the voice pipe and all wiring running along the mast. To guard against this possibility, Dreadnoughts fire-control system was comprehensively upgraded during her refits in 1912–13. The rangefinder in the foretop was given a gyro-stabilized Argo mount and 'A' and 'Y' turrets were upgraded to serve as secondary control positions for any portion or all of the main armament. An additional 9-foot rangefinder was installed on the compass platform. In addition, 'A' turret