Type 98 50 mm mortar

The Type 98 50 mm mortar is a smooth-bore, muzzle-loading weapon. The Type 98 designation was given to this weapon as it was accepted in the year 2598 of the Japanese calendar (1938)[2]

Type 98 50 mm mortar
Place of origin Empire of Japan
Service history
Used by Imperial Japanese Army
WarsWorld War II
Specifications
Mass21.77 kg (50 lb)
Barrel length650 mm (2 ft 2 in)[1]
Shell weight6.4 kg (14 lb 2 oz) Stick bomb
Caliber50 mm (1.97 in)
ActionManual
Elevation+40° Fixed
Traverse7°[1]
Maximum firing range455 m (498 yd)[1]

Design

The Type 98 50 mm mortar may be identified by the rectangular, sectionalized base plate, the fixed position of the bipod, the V slots painted white and located at 12 o'clock on both the barrel collar and the projection of the muzzle hoop and the marking which is on the outside of the container in which the weapon is packed. (This marking, which is read "Kyuhachi Shiki Totekiki" from right to left, means "98 Type discharger.")[2]

The propelling charge consists of black-powder increments packed in small silk bags. Each increment is approximately 3.75 inches long and 1.25 inches in diameter. A pull-type friction primer, 0.88 inch in length, equipped with a loop lanyard, is designed to fit into the primer seat, or touch hole.[2]

The mortar consists of three main parts the base plate, the bipod, and the barrel. It has a fixed elevation of about 40 degrees. Provision is made for a limited traverse. At the base of the tube is an offset primer seat. Two links, one on each side, extend from the barrel collar. A range slide, graduated from 0 to 60, may be clamped to the muzzle of the mortar.[2]

Firing system

To load, insert one or more powder increments in the muzzle. Place the stick of the stick bomb in the tube. Then, to aim, adjust the graduated range slide to the desired distance. This regulates the length of the stick extending into the barrel of the mortar. The greater the distance the stick extends into the barrel, the greater the range. The principle involved is similar to that employed in adjusting the range of the Type 89 50 mm grenade discharger. To traverse, loosen the two wing nuts that secure the bipod, and swing the bipod feet around the area in front of the base plate. Finally, to arm explosive charge, insert the two friction-type pull igniters in the holes provided in the base.[2]

Adjusting graduated range slide on Type 98 50 mm mortar of the charge. Connect each igniter by cord to one of the two links extending from the barrel collar of the mortar on each side. Insert a pull-type friction primer in the primer seat, which is on the side of the barrel near the base.[2]

To fire, pull the loop lanyard attached to the friction primer.[2]

Maintenance

The Type 98 50-mm mortar may be given the same care as would be given to US mortars. There is a cleaning brush which comes attached to the underside of the carrying box cover. The mortar is easy to disassemble. Unscrew the thumb screws and remove the bipod feet from the traversing plate; then remove the barrel assembly ball out of the socket in the base plate. Remove the collar which attaches the bipod to the barrel. To assemble the weapon, proceed in the reverse order.

Ammunition

At least three different types of projectiles can be fired from the Type 98 mortar. One is a finned Bangalore Torpedo and two are stick bombs. The stick bombs are composed of a hardwood stick 48 mm (1.9 in) diameter that fits into the barrel of the launcher and are reinforced with a metal cap at the bottom to withstand the stress of firing. The other end of the stick fits into a flange on the bottom of a rectangular head made from sheet steel and is fastened with nails or screws. The head is filled with either a rectangular block picric acid or with black powder. Two friction igniters fit into holes in the base of the stick bomb and the cords for these are fastened to either side of the launcher. When the mortar is fired the friction igniters are lit and a black-powder delay train starts giving a 7 second delay.[2]

Type Length Warhead size Weight Explosive weight Explosive type
Bangalore Torpedo 1.96 m (6 ft 5 in) Diameter: 48 mm (1.9 in) 8.2 kg (18 lb) 2.9 kg (6 lb 5 oz) Picric acid
Small Stick Bomb 69 cm (2 ft 3 in) Length: 171 mm (6.75 in) x Width: 110 mm (4.5 in) x Height: 110 mm (4.5 in) 7.1 kg (15 lb 11 oz) 3.2 kg (7 lb) Picric acid
Large Stick Bomb 65 cm (2 ft 1.5 in) Length: 110 mm (4.5 in) x Width: 159 mm (6.25 in) x Height: 159 mm (6.25 in) 7.7 kg (17 lb) 4.5 kg (10 lb) Black powder
  • 50 mm Bangalore Torpedo.
  • 50 mm Stick Bombs.

References

Notes
  1. Chamberlain, Peter (1975). Mortars and rockets. Gander, Terry. New York: Arco Pub. Co. p. 13. ISBN 0668038179. OCLC 2067459.
  2. War Department Special Series No 30 Japanese Mortars and Grenade Dischargers 1945

Bibliography
  • US War Department Special Series No. 19 Japanese Infantry Weapons December 1943
  • US War Department Special Series No 30 Japanese Mortars and Grenade Dischargers 1945
  • US War Department TM-E 30-480 Handbook on Japanese Military Forces 1 October 1944

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