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 gun as it was accepted in the year 2598 of the Japanese calendar ( 1938 ) 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 . " ) 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 . 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 . The Type 98 50 mm mortar fires a formidable stick bomb weighing nearly 10 pounds and containing an explosive charge of approximately 7 pounds of picric acid in rectangular blocks . The body of the bomb , made of sheet metal ( three - sixteenths of an inch thick ) , is rectangular in shape 4 1 / 2 by 4 1 / 2 by 6 1 / 2 inches ) and is painted black . A hardwood stick 21 inches long and 1 . 91 inches in diameter fits into a socket in the base of the body , and is held in place by nails or screws . The bottom end of the stick is covered with a metal cap . Two friction - type pull igniters , with black - powder delay trains giving a delay interval of approximately 7 seconds , fit into holes in the base of the charge . 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 are 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 . 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 . To fire , pull the loop lanyard attached to the friction primer . Ammunition . The stick bomb described above , is the only ammunition for this weapon that has been recovered to date . A recent report states , however , that a finned Bangalore torpedo may also be used . 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 .