Tail Pistol No. 17 Mks I - III (Obsolescent)

Description: This pistol employs three basic prinicples of operation. They are mecha-nical impact, chemical action, and anti-withdrawal action. The principal parts consist of the arming vanes, retaining balls, safety strips, sleeve, striker, ampoule, firing pin, and locking balls.

Operation: After the safety pin has been withdrawn and the bomb released, the arm-ing vanes rotate up and off in approximately eight revolutions. On impact, the striker weight moves down against the hammer, forcing it against the crusher, which smashes the ampoule against the perforated disc and ampoule seating. Two other things occur si-multaneously with this action. The thin brass safety spider moves down, the four protru-ding end being pulled free from above the safety collar, and the locking and cocking pel-lets move down, the former pulling the sleeve with it. As the sleeve clears the two lock-ing balls, their spring forces them into the narrower parts of the grooves in which they ride and lock the lower part of the pistol body in the exploder. Since the safety collar is no longer retained by the safety spider, the two safety strips resting against it are free to be forced up. The acetone acts on the delay disc, the time of the action being pre-determined; and as the disc is dissolved or softened, the timing spring forces the firing-pin release cup up. Two projections on this cup force the safety strips up with the cup. These strips could not rise until after impact, when the safety spider pulled free from above the safety collar. As the firing-pin release cup rises, the firing-pin retaining balls are forced out by the cocked firing pin into the gradually increasing area, until they fi-nally clear the groove in the upper part of the firing-pin spindle, and release the firing pin to be forced against the detonator.

If an attempt should be made to extract the pistol after it has been dropped and the locking balls have been forced by their springs between the narrow part of the groove and the exploder, such an attempt would merely tend to bind the lower part of the pistol more firmly, the result being that the upper part would be unthreaded and the firing-pin release cup pulled clear of the firing-pin retaining balls. As the balls clear the groove in the firing-pin spindle, the cocked firing pin would be forced against the detonator and detonate the bomb. Approximately one or two turns would activate the anti-withdrawal functioning of the pistol.

Remarks: The delays which may be incorporeated in this pistol, and the identifying color of the groove in the lower body extension housing the firing pin head, are as fol-lows:

No. 17 Mk I – 30 min. – Top red, bottom green

No. 17A Mk I – 1 hr. – Top red, bottom black

No. 17B Mk I – 2 hr. – Top red, bottom yellow

No. 17D Mk I – 3 hr. – Top red, bottom blue

No. 17E Mk I – 6 hr. – White

No. 17F Mk I – 8 hr. – Yellow

No. 17G Mk I – 12 hr. – Green

No. 17H Mk I – 18 hr. – Red

No. 17J Mk I – 24 hr. – Black

No. 17K Mk I – 36 hr. – Light blue

The delay is engraved in the pistol body just above the colored groove. The letter ad-ded to the fuze designation also indicates the delay. The Fuze Mk II has the same letter and time designations as the Mk I, nut the anti-withdrawal device is not present on the latter. The Mk III is similar to the Mk II, except that it has a lighter spider, and the safe-ty pin hole is increased in diameter. The fins of bombs using this pistol and the arming vanes are usually painted red. Early fuzes has a lead anti-withdrawal lug instead of lock-ing balls.

This pistol should never be withdrawn from a bomb that has been dropped form an air-craft.

Figure 122 - Tail Pistol No. 17 Mk I