Unarmed Position

MT M43 Series. The original M43 fuze was developed to fulfil the requirement for a single-purpose MT fuze for antiaircraft use with medium caliber shell fitted with the same booster as other standard fuzes. All modifications have the contour which is characteristic of modern design fuzes. They provide for time setting to 30 seconds and are without impact element (See Fig 1-89) The fuze body for the M43 to M43A4 fuzes is in three parts an upper cap, a movable lower cap, and a fixed base (W). 

The lower cap holds the setting pin (B) and a hammer (D) device which releases the 

The fuze is set by means of a fuze setter, the lower cap being turned in a counterclockwise direction as viewed from the point of the fuze to increase the setting, and clockwise to reduce it. In the case of early M43A1 fuzes, it is necessary to remove the pull wire before setting the fuze. This can be done readily by pulling the end of the wire from the hole in the lower cap and sliding the wire off the end of the fuze 

1 Fuze will not function if set below this figure 2 Upper cap painted red 

3 Fuzes of late manufacture without pull wire 

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Fuzes contain safety devices that tend to prevent functioning until after the fuze has been subjected to centrifugal and setback forces, after the round is fired. In the so-called bore-safe fuzes, the path of the explosive train is interrupted so that, while the projectile is still in the bore of the weapon, premature expln is prevented should any of the more sensitive fuze elements (such as primer and/or detonator) start to function. Interruption is usually achieved by inserting out-of-line components or interrupter blocks or slides. Although this leaves the fuze in an unarmed position, it would not be considered safe in handling or shipping, unless the fuze was not provided with safety devices such as safety wires or cotter pins. These outside devices must be removed prior to inserting the fuzed round of ammunition into gun barrel, but the fuze will still be unarmed because some of its inside parts are not free to move to their proper positions so that the fuze may operate in its intended manner... 

The nose (B) holds the firing pin (C) and screws into the upper end of the head (H) in such a manner as to leave a recess below the firing pin (C). Half-blocks (E) and a coiled spring (D) are positioned in the recess to hold the pin (C) in an unarmed position prior to firing. The front end of the nose (B) is closed with a thin A1 disk (A) for protection against foreign matter or air resistance. 

Before release. Before the fuzed bomb is released, the arming wire prevents the arming vane from turning. The end of the firing pin in the hole in the rotor holds the rotor in the unarmed position with the primer out of alignment with the arming pin and detonator... 

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