Description: Two variations of this device have been found that differ only in the color of their plastic case and the diameter of their firing pin retaining wire. One model has a brown, opaque, plastic body and a retaining wire 0.035 inch in diameter, while the other has a transparent plastic body and a retaining wire 0.042 inch in diameter.

The body of the device is internally partitioned into three sections, and is closed at each end by a threaded plastic closing plug. The upper section a chemical tank, is empty ex-cept for a small anchor block to which the firing pin retaining wire is secured. A small screw holds the anchor block in position. A compressed firing spring is contained in the center section and continues into the lower section where is seated against the firing pin. The firing pin is held in position by the firing pin retaining wire. A gum-like substance which covers the top of the firing pin spring seals the upper section against possible leakage of the chemical that activates the device. The only safety device used is a light metal sleeve inserted in the lower section between the firing pin and the detonator. The gaine is threaded into the bottom closing plug.

A small bottle of the activating chemical, cupric chloride, is carried in a separate card-board container.

Employment: Not known. Recovery of a hand auger of approximately the same diameter as the gaine with the device strongly suggests that it can be used in preparing wells in almost any explosive charge to receive the device.

Operation: Remove the safety sleeve and replace the bottom closing plug. Pour the cu-pric chloride into the top of the device and replace the top closing plug. The resulting chemical reaction between the cupric chloride and the firing pin retaining wire weakens the wire, which finally snaps allowing the spring-loaded firing pin to impinge upon the de-tonator.

Firing tests conducted with the transparent firing device using varying amounts of che-mical gave the following results:

Corresponding tests with the brown device should give a shorter delay due to the smaller sized firing pin retaining wire is uses.

To render safe: Destroy in suit if possible or remove the device from the charge and dis-pose of it immediately.

Figure 193 – Time Firing Device Mk 1.