Nathan:

The earlier U.S. Navy contact exploder (pistols) mechanisms used 65 grains of fulminate of mercury for its detonator, (with two Winchester caps)and a bored-out tetryl booster (ounces?) which detonated the TNT/TORPEX main charge. A bim-bam-boom effect occurred.

A solid brass gear-drive mechanism was driven by a brass turbine-type impeller mounted in a "groove" at the bottomside of the warhead. Forward motion of the torpedo though the water rotated the drive shaft and via pinions and a vertical shaft, and rotated the "bull-gear" atop the mechanism. This action drove the fulminate of Mercury detonator upward and out of its "safety chamber, into the cavity of the tetryl booster, which was positioned atop the safety chamber and fitted closely in a molded pocket of the warhead.

Upon impact with the target, a brass firing ring at its base was displaced by its decelerationand tripped fingers allowing a spring-loaded firing pin block to shoot vertically, guided by two lugs, (on each side of this block) to ride up two vertically-mounted brass guide-posts.

Then the firing pin struck the Winchester caps, ignited the Fulminate of Mercury
detonator, detonating the Tetryl booster and finally the main charge. And then all hell breaks loose.

The purpose of this gear-train is to allow the firing vessel to be be a safe distance away in case of a an early detonation by any means, such as gunfire, exploding depth charges or contact with anything not determined to be the target.

The MKVI magnetic influence exploder mechanism, on nthe other hand, used a heavy copper-wound pickup coil and pickup rod, which was positioned fore and aft through the bored-out coil assembly. This unit retained the same contact feature described above, but had an electronic feature as well.

An electrical generator, mounted on the mechanism's base-plate, was driven by thar same brass impeller. It charged an 8 microfarad condenser/capacitor, which was the stored electrical energy that would fire two "squibs" and detonate the Fulminate of Mercury detonator, and start the chain reaction when the magnetic signal from the target was strong enough to fire a Thyratron tube, thus releasing the stored electrical energy in the capacitor.

I'll not get into the causes of failure of this exploder, nor the on-site remedy. That's
entirely another subject.

I hope this answers your question about U.S. exploder mechanisms anyway.

Later,

ROBERT M.