"Explosive force" is rather hard to define. It involves several effects including the heat of the explosion, the velocity of the explosion and the related detonation wave, the pressure created by the explosion, and the gases produced by the explosion. the result of all these forces is defined as "Brisance" which is the shattering effect on material caused by the explosives sudden release of energy.

You really need to do field experiments with various combinations of chemicals and substances to find what gives you the best "bang for the buck" and could be safetly handled aboard a submarine. WW II German torpedo warheads contained the explosive "Hexanite" which was a combination of that old standby TNT, HND (hexanitrophenylamine) and powdered aluminum.

research conducted by the German and American Navies in the 20's and 30's led them to the conclusion that if the torpedo warhead could be detonated underneath the target brisance caused by the explosive force would be greatly enhanced. this led to the development of magnetic influence exploders by both Navies. The German Navy recognized fairly early that using the magnetic field of the target ship to detonate the torpedo exploder was unworkable and returned to use of contact exploders. The U. S. Navy continued to use the Mark 6 magnetic influence exploder with the Mark 14 air-steam torpedo until early 1943 when magnetic influence was finally abandoned. the Mark 14 torpedo and the Mark 6 exploder soldiered on into the early 1980's in the USN.