A heavy, short-barreled mortar, pendulum- mounted, for determining the relative power of explosives; a small sample of a test explosive is placed in the detonation chamber and a projectile is located forward of the charge; upon detonation the projectile is driven into a sand bank and the mortar swings through an arc; a marker records the maximum weight of the test explosive required to produce the same rise as 10 grams of TNT.