81-MM BARRAGE MORTAR
The capture of an 81-mm barrage mortar has been reported. Sometimes called a “spike” mortar, this type of weapon consists of a mortar tube on a wooden base block on the bottom of which is a large metal spike. When fired, the barrage mortar shell, after reaching a definite range, expels a series of parachute-supported high explosive charges which detonate by time fuzes. Because of the crude spike and block arrangement for emplacing it in the ground, the mortar is considered highly inaccurate. It is believed to have been developed for use against low-flying aircraft, or for firing over the heads of hostile ground troops. The Japanese are known to have a standard 70-mm barrage mortar, but the 81-mm variety found at Ormoc is the first of its caliber to be reported. 
----------------------------------------------------------------- The AA mine discharger was a Japanese anti-aircraft weapon of the Second World War. The device was a simple tube like an infantry mortar of 70 mm (2.8 in) or 81 mm (3.2 in) caliber. Instead of a standard mortar bomb, the projectile was a tube containing seven individual mines, each approximately 11/16ths of an inch in diameter (18 mm) and 3 inches (76 mm) long. Each mine was equipped with its own parachute. When fired, the mortar threw the shell to a range of 3,000 to 4,000 feet (900 to 1,200 m) and a maximum altitude of approximately 600 m (2,000 ft). The shell ejected the mines at the top of its arc. They would then float down on their parachutes. They were fused to detonate on contact or after a fixed time period, damaging nearby aircraft. The projectile could alternatively be launched using a standard Type 11 70 mm infantry mortar.
The weapon could also be used like a simple cluster bomb, by firing over enemy troops.