Fuzes: Type 3 electric firing device, B-3 (a).

Over-all length: 62 inches.

Length of body: 30 3/8 inches.

Diameter of body: 11 3/4 inches.

Thickness of wall: 1/2 inch.

Material of wall: Steel.

Type of suspension: Horizontal.

Suspension lug: Normal Navy suspension lug.

Color and markings: Grey over all. Green tail struts. No color band on nose.

Length of tail: 32 inches.

Width of tail: 16 1/8 inches.

Width of tail fins: 7 1/5 inches.

Dimensions of tail struts: Length, 13 4/5 inches; width, 2 1/4 inches; thickness, 1/12 inch.

Material of tail: Steel.

Type of filling: Type 98 explosive, cast.

Weight of filling: 175 pounds.

Total weight of bomb: 378 pounds.

Charge/weight ratio: 33 percent.

Construction of body: The bomb consists of a nosepiece, barrel, and tail assembly.

The nose of the bomb is blunt. A flat metal plate is filled into the forward end of the bar-rel and welded there. The plate is drilled centrally and a gaine pocket is welded in the hole. A  flange 3 7/8 inches long, 7/32 inch thick and of the same outer diameter as the barrel is welded to the forward end of the barrel. The flange is pierced by four 1/2-inch holes just aft of the forward end.

The barrel is of tubular steel construction.

The tail cone is held by 1 row of 18 plug welds and a continuous weld to a coupling ring which fits inside the barrel. The ring is held in the barrel by 2 rows of screws numbering 40 in all. There is a standard tail fuze pocket at the apex of the tail cone.

Construction of tail: Four Navy type fins are spot-welded to the tail cone. The fins are braced by a single set of box-type struts.

Operation: The type 3 electric firing device is an influence fuze, operated by a photo-electric cell, which is activated by reflection of a beam of light projected from the fuze, and reflected from the target. Aerial burst at an altitude of 7 meters or above was desi-red by the designers. Fifty percent accuracy was considered to have been attained.

Figure 68 - Type 3 No. 25 Mk 31 Bomb Model 1.