USNBD, British Bombs and Fuzes, Pyrotechnics, Detonators; Section I - British Bombs and Pyrotechnics; Miscellaneous Bombs: 250 lb. "B"

U.S.N.B.D. - BRITISH BOMBS AND FUZES; PYROTECHNICS; DETONATORS

MISCELLANEOUS BOMBS


		BRITISH BOMB
FUZING	Tail Fuze No. 850	250 LB. "B"
COLOR & MARKINGS	Dark grey overall; ½" red
	band 3" from nose; ½"
	green band 9-½" from
	nose.	Mk. IV
TAIL NO.	No. 23, Mk I (Mk III body)
OVERALL LENGTH	72 in.	(Service)
BODY LENGTH	42 in.
MAX. BODY DIAMETER	14.3 in.
WALL THICKNESS
TAIL LENGTH	28 in.
TOTAL WEIGHT	240 lb. (approx.)
CHARGE/WEIGHT RATIO	40% (approx.)

BODY CONSTRUCTION:

The bomb consists of a truncated cone-shaped charge case with a concave nose welded on, a buoyancy chamber secured to the charge case by twelve nuts, and a clip-on tail. A convex nose attached can be fitted to the nose by means of three brac-kets equi-spaced around the edge of the nose. The buoyancy chamber has twelve hand clearance pockets around the forward end to permit access to the twelve bolts securing the charge case. Internal reinforcements are spot welded to the interior for-ward half of the buoyancy chamber and two circular stiffeners extend athwartships through the chamber, spot welded to the chamber wall. An exploder tube extends cen-trally through the buoyancy chamber and charge case, welded at the rear ot the joint ring fitting inside the fuze pocket, and supported by the stiffening ring in the middle of the buoyancy chamber.

TAIL CONSTRUCTION:

No. 23 Mk I tail, used on the Mk III body, consists of a tail cone with cylindrical strut secured by four fins riveted to strut and tack welded to tail cone. Tail assembly attached to body by spring clips, the assembly coming off when bomb enters water.

FUNCTIONING:

On striking the water, the nose attachment is dished in and the tail breaks away. When the tail breaks away it uncovers a wheel shaped disc on the base of the bomb. This is the contact disc, to which are attached three chains, the other ends being fastened to the support ring on the bomb base. If these chains are tight the fuze is arming because the contact disc rises during the arming process. If the bomb fails to hit a ship upon rising, it sinks after a short period.

SUSPENSION:

Suspended by a single lug secured by four screws threaded into a suspension lug stiffener and boss spot welded to the interior of the buoyancy chamber.

EXPLOSIVE CONTENTS:

Exploders: C.E. exploders in central tube.

Filling: 113.2 lbs. Torpex 2, with 3.25 lbs. T.N.T. topping in aft end of charge case.

REMARKS:

(1) This bomb is designed to be dropped in front of ships underway, and to rise and detonate on contact with the ship's bottom.

(2) The concave nose portion of this bomb is designed to give better under-water ballistics rather than Munroe effect.