a ceiling of less than ; horizontal range was at an elevation of 35.7°. The single-shot SK C/30 fired projectiles at a muzzle velocity of at a rate of 30 rounds per minute. The boats were also fitted with a pair of 65-caliber C/30 AA guns on the bridge wings. The gun had an effective rate of fire of about 120 rounds per minute. Its projectiles were fired at a muzzle velocity of which gave it a ceiling of and a maximum horizontal range of . Each boat carried 2,000 rounds per gun. The boats were also equipped with six above-water torpedo tubes in two triple rotating mounts and could also carry 30 mines (or 60 if the weather was good). The boats used the G7a torpedo which had a warhead and three speed/range settings: at ; at and at . Many boats exchanged the 3.7 cm gun for another 2 cm gun, depth charges and minesweeping paravanes before completion. Late-war additions were limited to the installation of radar, radar detectors and additional AA guns. Ships Service Although the first few boats were completed at the end of 1939, maintenance problems with the boilers and modifications to the bridge and the normal issues associated with working up boats of a new class, kept them in German waters until mid-1940. Assigned to the 5th Torpedo Boat Flotilla, T2, T7 and T8 began escorting minelayers as they laid a minefield in the North Sea in August. By the end of the month, T1, T2 and T3 were assigned to the 1st Torpedo Boat Flotilla while T5, T6, T7 and T8 were assigned to the 2nd Torpedo Boat Flotilla. Both flotillas continued to escort minelayers in the North Sea and the English Channel and the Straits of Dover. T12 was transferred to Norway for convoy escort duties in September. T2 was damaged by British bombers on 9 September and returned to Germany for repairs. T3 was sunk by British bombers nine days later, although she was refloated in 1941 and towed back to Germany. By November the 1st and 2nd Torpedo Boat Flotillas with T1, T4, T6, T7, T8, T9 and T10 between them had transferred to Stavanger, Norway. On 6 November they departed in an attempt to attack two coastal convoys that had been spotted off the Scottish coast, but they ran into a British minefield that sank T6 and they returned