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| BRITISH EXPLOSIVE ORDNANCE |
| Part 1 - Chapter 8 |
| Antisubmarine Bombs |
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A.S. 250-lb. Mks I, II, and III (Obsolescent) and Mk IV (Service) |
| Data |
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Fuzing |
Mks I - III, Nose Fuze No. 32; Mk IV, Tail Pistol No. 28 or No. 30 |
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Color markings |
Dark green over-all; ½-in. red band 1 in. from nose; 1-in. light green band 4½ in. from nose |
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Tail No. |
Mk IV - No. 8 Mk I |
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Over-all length |
Mk III, 59 in.; Mk IV, 58 in. |
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Body length |
Mk III, 42 in.; Mk IV, 35.2 in. |
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Body diameter |
Mk IV, 11.35 in.; Mk III, 11.2 in. |
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Wall thickness |
Mks III and IV, 0.14 in.; Mks I and II, 0.125 in. |
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Tail length |
Mk IV, 23.4 in. |
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Tail width |
11.0 in. |
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Total weight |
Mk IV, 243 lb. |
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Charge/weight ratio |
Mk IV, 55% |
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Body Construction: The Mk IV body consists of a hollow nose forging or casting and a cast or forged tail adapter, welded to a sheet-steel casing. The hollow, flat nose is threaded to take a solid nose plug which is secured by a locking screw. The casing is made of two parts, welded together longitudinally. The tail adapter receives the exploder container, which is locked and sealed in position, and houses the detonator holder and pistol. |
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The Mk I - III bodies have the nose fitted with an adapter for a nose fuze. Internal strengthening bands are welded to the body, which has no tail adapter. A ballistic cap screws on the nose to prevent ricochet. |
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Tail Construction: In the Bomb Mk IV, the tail assembly consists of a sheet-metal cone with a cylindrical strut attached to it by four fins. The assembly is secured to the tail adapter by four spring clips on the cone. A reach rod, with arming vanes attached to after end, extends through the cone and engages the arming fork of the tail pistol. |
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The tails of the Bombs Mk I - III consist of a cylindrical strut atteched by four fins to a dome-shaped tail cone, and secured to the bomb by a central bolt. |
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Suspension: The bomb is horizontally suspended by a single lug, secured by screws projecting through the case and into a steel-block support pad welded to the interior of the body. |
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Explosive Components |
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Detonator – (See Part 2, chap. 4, Detonators.) |
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Exploders – C.E. pellets. (Early marks had C.E. and TNT.) |
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Filling – Mk IV, 134 lb. RDX/TNT or 132 lb. TNT (when RDX/TNT is used, bomb has ½-in. nose topping and 1-in. base topping of TNT); Mk III, 149 lb. Baratol or 140 lb. TNT. |
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Remarks: These bombs are designed to give maximum blast effect for use against submarines. The Tail Pistol No. 30 with a needle striker is to be used in the Bombs Mk IV A/S bombing. The Tail Pistol No. 28 can be used in place of the No. 30 for land bombard-ment. |
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Figure 31 – A.S. 250-lb. Bomb Mk III |
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