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| Japanese Explosive Ordnance – Army Ammunition – Navy Ammunition |
| Chapter 4 – Section 3 |
| ARMY MORTARS |
| 81-mm Parachute H.E. Mortar |
| Weight complete round: 3.87 pounds. |
| Weight main charge: 4 ounces. |
| Explosive components: |
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Main charge: |
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RDX (1 block). |
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TNT (2 blocks). |
| Over-all length: 21.25 inches. |
| Length of shell (less propellant container and nose plug): 18.5 inches. |
| Diameter of shell body: 1.5 inches. |
| Diameter of fins: 3.19 inches (81 mm). |
| Diameter of H.E. cylinder: 1.37 inches. |
| Length of H.E. cylinder: 7.0 inches. |
| Color: Black over all with an unpainted wooden plug in the nose. |
| Weapon in which used: Standard 81-mm smooth-bore mortar. |
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Description: This mortar shell is a black steel tube with an ogival wooden block sealing the forward end. Six fins which give the shell an 81 mm diameter are spot welded along the after part of the tube. A steel disc drilled through the center for the delay lead-in is welded to the tube 1/2 inch from the base. Forward of the disk is a 5-inch wooden block through the center of which runs the 12-second black powder delay element. The for-ward end of the wooden block contains the ejection charge. The H.E. cylinder and para-chutes are located forward of the ejection charge. The cylinder consists of a steel case, a central tube containing the 45-second self-destruction delay train, a friction igniter, and three cylindrical explosive blocks fitted around the central tube. The booster fits in the forward block. The parachute which supports the cylinder is secured to a small fixed U-bolt on the cylinder by nine short (13-inch) shrouds. A second parachute above the first is secured to the friction igniter by a line 32 feet 4 inches long. This line leads through a central hole in the lower parachute. |
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The tinned steel propellant container is 81 mm in diameter and 1 inch deep. A neck on the container cover fits into the base of the mortar shell and is secured by three small screws passing through the sides of the shell and the neck of the cover. |
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Operation: When the shell is fired, the flash from the black powder primer ignites the propellant and the 12-second delay train. Setback shears the small screws securing the propellant container to the shell, and when the force of the propellant is expended the container falls free. Twelve seconds after firing, the delay train ignites the ejection char-ge forcing the H.E. cylinder and parachutes out the forward end of the shell. The 45-se-cond self-destroying delay train is also ignited by the ejection charge. Planes striking the 32 foot parachute cord which is attached to the igniter will cause it to explode the H.E. cylinder. After 45 seconds, the self-destroying element detonates the cylinder. |
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Figure 305 – 81-mm Parachute High-Explosive Mortar. |
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