21cm Mörser 18

The 21cm Mörser 18 was one of two parallel Krupp designs using a double recoil system, and was phased out in 1942 in favour of the longer ranged 17cm Kanone 18.

21cm Morser 18 from the front

The majority of innovations in the Mrs 18 came in the carriage, which Krupp called the Morserlafette. This began with the double recoil system. The first part of this was a standard recoil system attached to the barrel, which absorbed the first part of the recoil forces. The barrel was carried on a carriage that was mounted on rails on the main travelling carriage. This slid backwards when the gun was fired, absorbing the rest of the recoil force. This meant that the main carriage hardly moved at all when the mortar was fired, making it easier to keep up a rapid, accurate bombardment. A second innovation was to provide a small firing platform that could be attached under the front of the carriage. Without the mortar could traverse through 16 degrees, with it a single man could rotate it through 360 degrees.

The Mrs 18 had a long barrel, with the recuperator cylinder mounted above it, and carried on a slide attached to the upper carriage. Equilibrators were mounted diagonally on either side of the barrel, just ahead of the trunnions, to make it easier to balance the gun. It had a falling wedge breech block, which used the cartridge case to seal the breech and prevent gasses escaping when the mortar was fired.

The Mrs 18 had to be split into two loads to be moved - the barrel and the carriage. A series of ramps and winches were provided to make this job easier. It was also possible to tow the weapon over short distances as a single load.

The 21cm Mrs 18 was the first of the two to enter service, arriving in 1939. It was given a high production priority, with work split between Krupp and Hanomag of Hannover. A number of specialised shells were developed for the mortar, including a dedicated concrete piercing shell for use against strong fortifications, ‘stick bombs’ and fin stabilized rounds.

When the 17cm Kanone 18 entered service in 1941 it soon became clear that its shells were almost as damaging as the much heavier mortar shells, and the reduction in damage was more than made up for by the massive improvement in range - up from 16,700m on the mortar to 29,600m on the cannon. As a result production of the Mrs 18 entered in 1942, in favour of the K 18. Even so the Mrs 18 remained in service to the end of the war, and remained an effective weapon.

German Heavy Artillery Guns 1933-1945, Alexander Lüdeke. Despite the title actually covers light, medium and heavy artillery as well as mortars and anti-tank guns (excludes railway guns, flak and rocket launchers). Each gets a useful write-up, supported by stats and at least one photo. Covers German-built guns and the many types captured and used by the Wehrmacht. [read full review]

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