35.5-cm Haubitze M.I
In 1935 the German army asked Rhein metall to produce an enlarged version of its 24-cm K 3, and although the design of that gun was still at an early stage the Rheinmetall company went ahead and produced a new design with an actual calibre of 355.6mm (14 in). The first example was produced ready to enter service in 1939, and emerged as a scaled-up version of the 24-cm (9.37-in) design. The new weapon was designated the 35.5-cm Haubitze M.1 (35.5-cm H M.I) and incorporated many of the features of the 24-cm (9.37-in) design including the double-recoil carriage. The weapon was even carried in six loads, but an extra load had to be involved for the special gantry needed to assemble and disassemble the massive weapon. This gantry used electrical power from a generator carried on the same 18tonne halftrack tractor that towed the disassembled gantry. Other 18-tonne halftracked tractors were also used to tow the other components; these were the cradle, top carriage, barrel, lower carriage, turntable and rear platform.
There appears to be no record of how long it took to get the H M. l into action, but the time involved must have been considerable. It is known that the weapon was used by only one unit, namely l Batterie der Artillerie Abteilung (mot) 641. This motorized artillery battery was certainly involved in the siege of and assault on Sevastopol, but its exact whereabouts at other times are not certain.
In fact the H M. l is something of a mystery weapon, and there are still a number of unknown facts regarding its service career. Even the exact number produced is uncertain. It is known that the weapon was manufactured at Rheinmetall's Dusseldorf factory, but the number completed varies from three to seven depending on the reference consulted. The projectiles fired included a high explosive shell weighing 575 kg (1,267.6 lb), and there was also a concrete-piercing shell that weighed 926kg (2,041.5 lb). Four charges propelled these shells, It is known that it was possible to effect 360° traverse on the carriage platform by using power jacks.
For all its weight and bulk, the H M. l had a range of only 20850m (22,800 yards), so the efficiency of the weapon must have been questionable even at the time. Looking back it now seems doubtful that the considerable investment of money, manpower and equipment in a howitzer with such a limited range was generally not worth the efforts involved. But the H M. 1 fired a shell that must have been devastating in effect when it landed on target. Even the strongest fortification would be hard put to remain operational after a few hits from such a shell, and this no doubt made the howitzer a viable weapon for the Germans. But the truth was that during World War II there were few such targets for the H M. l to pulverize, and the only time that the howitzers were put to any great use was during the siege of Sevastopol. There are records of these howitzers firing 280 rounds, though they must have taken some time to accomplish this, for the rate of fire of the H M. l was at best one round every four minutes.
Specification 35.5-cm H M.1
Calibre: 356.6 mm (14 in)
Length of piece: 10.265 m (33 ft 8.1 in)
Weight: travelling 123500 kg (272,271 lb) and in action 78000 kg (171,960 lb)
Elevation: +45° to +75°
Traverse: on platform 360° and on carriage 6°
Muzzle velocity: 570 m (1,870 ft) per second
Maximum range: 20850 m (22,800 yards)
Shell weight: HE 575 kg (1,267.6 lb) and anti-concrete 926 kg (2,041.5 lb)