British Explosive Ordnance - Anti-Submarine and Buoyancy Bombs, and Aircraft Depth Charges

British Explosive Ordnance

 Semi-Armor Piercing and Armor Piercing Bombs Introduction

AS bombs, ranging from 100 to 600 pounds, are at present in service use.  They are thin-walled bombs, having a high charge/weight ratio for maximum blast effect on, or under, water.  Aircraft depth charges are used by the British as alternatives for these bombs.

Earlier marks of the 100, 250, and 500 pound bombs employed a Nose Fuze No.32, but later marks incorporate a pistol/detonator combination at the tail only.  The 600 pound bomb uses a tail fuze.

These bombs are painted green overall, and may be filled with Torpex, TNT, or Minol.  Their charge/weight ratio is from 50 to 80 percent, depending on the individual bomb and the filling.  The 100, 250, and 500 pound bombs are streamlined in shape.

AS 100lb Mks I-IV (Obsolescent), and Mk VI (Service)

  

Overall length: 42 inches (Mk VI is several inches longer with nose attachment)

Body length:
-Mks I-III: 31 inches
-Mks IV-VI: 24.08 inches

Body diameter: 8.05 inches
 Wall thickness: 0.11 inches

Tail length: 18 inches
Tail width: 8 inches

Total weight: 98 pounds
Charge/Weight ratio: 45% (approx.)

Fuzing:
-Mks I-III: Nose Fuze No.32
-Mk IV: Tail Pistols No.28 or No.30
-Mk VI: Tail Pistol No.30, or Tail Fuzes No.875 or No.895

Tail No:
-Mks IV: No.7 Mk I
-Mk VI: No.56 Mk I

Color and markings:  Dark green overall
1/2 inch red band 1 inches from nose,
1 inch light green band 4 inches from nose.

  

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 nose is threaded to take a solid, flat 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.

The Mk III body has a nose fitted with a nose fuze adapter, three internal strengthening rings, and a tail adapter.  A ballistic cap screws onto the nose to prevent ricochet.

In the Mk VI body, the nose plug and a cup-shaped nose attachment are welded on.


Tail Construction: The Bomb Mk IV uses a Tail Assembly No.7 Mk I which consists of a sheet-metal tail cone with a cylindrical strut attached by four fins.  It is secured to the tail adapter by four spring clips on the cone.  The tail assembly also has a reach rod, with arming vanes on the after end, which extends through the tail cone to engage the arming fork of the tail pistol.

The tail of the Bomb Mk III consists of a cylindrical strut, attached by fins to a dome, which is secured to the bomb by a central bolt.

The Bomb Mk VI uses a Tail No.58 Mk I, which is secured by four locking screws threaded through four cone-securing bosses welded on at an angle to tail cone.  The screws thread inward and aft to engage slots in the bomb body.


Suspension: The bomb is horizontally suspended by a single lug, which is secured by screws projecting through the case and into a steel-block support pad welded to the interior of the body.
  

Explosive Components:
Exploders: CE

Filling:
-Mk IV: 45lb RDX/TNT 60/40 or 44lb TNT
-Mk VI: 49lb Torpex (when filled with Torpex, a topping of TNT is added at the nose and base)

Remarks: The Tail Pistol No.30 with needle striker is to be used in the Bomb Mk IV for AS bombing.  The Pistol No.28 can be used in place of the No.30 for land bombardment.

The Bomb Mk V was never produced.

AS 250lb Mks I, II, and III (Obsolescent) and Mk IV (Service)
   

Overall length:
-Mk III: 69 inches
-Mk IV: 58 inches

Body length:
-Mk III: 42 inches
-Mk IV: 35.2 inches

Body diameter:
-Mk III: 11.2 inches
-Mk IV: 11.85 inches
  

Wall thickness:
-Mks I and II: 0.125 inches
-Mks III and IV: 0.14 inches

Tail length: Mk IV - 23.4 inches
Tail width: 11 inches

Total weight: Mk IV - 243 pounds
Charge/Weight ratio: Mk IV - 55%

Fuzing:
-Mks I-III: Nose Fuze No.32
-Mk IV: Tail Pistols No.28 or No.30

Tail No: Mk IV - No.8 Mk I

Color and markings:  Dark green overall
1/2 inch red band 1 inches from nose,
1 inch light green band 4 and 1/2 inches from nose.

  

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.

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.


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 reacdh rod, with arming vanes attached to after end, extends through the cone and engages the arming fork of the tail pistol.

The tails of the Bomb Mk I-III consist of a cylindrical strut attached by four fins to a dome-shaped tail cone, and secured to the bomb by a central bolt.


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.
  

Explosive Components:
Exploders: CE pellets. (Early marks had CE and TNT)

Filling:
-Mks III: 149lb Baratol or 140lb TNT
-Mk IV: 134lb RDX/TNT or 132lb TNT (when RDX/TNT is used, bomb has 1/2-inch nose topping and 1-inch base topping of TNT)


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 for A/S bombing.  The Pistol No.28 can be used in place of the No.30 for land bombardment.

AS 500lb Mks I-IV (Obsolescent)
   

Overall length:
-Mks I and II: 74 inches
-Mk III: 76 inches
-Mk IV: 72.5 inches

Body length:
-Mks I, II, and III: 53 inches

 -Mk IV: 50 inches

Body diameter:
-Mks I and II: 14 inches

 -Mks III and IV: 14.8 inches

 Wall thickness:
-Mks I and II: 0.16 inches

 -Mk III and IV: 0.18 inches

 Tail length: Mk IV - 24.2 inches
 Tail width: Mk IV - 14 inches

Total weight: Mk IV - 490 pounds

Charge/Weight ratio: 62-64%
 Mk IV: 58%

Fuzing:
-Mks I-III: Nose Fuze No.32
-Mk IV: Tail Pistol No.28 or No.30

Tail No: Mk IV - No.9 Mk I

Color and markings:  Dark green overall,
1/2 inch red band 1 inch from nose,
1-inch light green band 6 inches from nose.

  

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 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.

The Mk I-III bodies have the nose of the bomb 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.


Tail Construction: The Tail Assembly No. 9 Mk I 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 the after end, extends through the cone and egages the arming for of the tail pistol.

The tails of the Bombs Mks I-III consists of a cylindrical strut attached by four fins to a dome-shaped tail cone, and secured to the body by a central bolt.


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.
  

Explosive Components:
Exploders: CE pellets. (Earlier bombs had CE and TNT)

Filling:
-Mks III: 291lb TNT or 308lb Baratol
-Mk IV: 282lb TNT or may be filled with RDX/TNT (when RDX/TNT is used, bomb has 1/2-inch nose topping and 1-inch base topping of TNT.


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 for A/S bombing.  The Pistol No.28 can be used in place of the No.30 for land bombardment.

AS 600lb Mk I (Service)

Overall length: 56.7 inches
Body length: 36 inches (w/o nose attachment)
Body diameter: 17.5 inches

 Wall thickness: 0.125 inches

  Tail length: 20.5 inches

 Tail width: 17.5 inches

Total weight: 550 pounds
 Charge/Weight ratio: 80% (approx.)

Fuzing: Tail Fuze No.862

Tail No: No.36 Mk I

Color and markings:  Dark green overall,
1/2 inch red band and 1-inch light green band around body.

  

Body Construction: The body consists of three pieces welded together; a concave nose, parallel sides, and a tapered base to receive the clip-on tail.  The after end is closed off by the closing plate, which houses the exploder container.  A round nose cap, attached to the nose for streamlining during air travel, breaks off on impact, giving the bomb an unstable trajectory, and so preventing ricochet.


Tail Construction: The clip-on type tail consists of a cylindrical strut secured to the tail cone by four fins.  The tail cone is constructed of four pieces and is held together by three rivets only.  There is no reach rod extending through the tail cone, as the fuze is not the arming-vane type.  The tail breaks off on impact with water, contributing to the unstable trajectory of the bomb.


Suspension: The bomb may be suspended from British planes by the single lug, or from US aircraft by the dual lugs on either side of the single lug.  when either dual lugs or the single lug are used, the remaining lug screw holes are closed by transit screws.
  

Explosive Components:
Exploders: CE

Filling: 432lb of Minol II or 439lb Torpex. (1/2-inch layer of TNT at base when filled with Minol or Torpex)


Remarks: The fuze is fitted in an anticounter-mining chamber.





  

Aircraft Depth Charges Introduction


The depth charges included in this section are those dropped from aircraft in antisubmarine warfare.  Only one size, the 250-pound is currently in use.  They are normally carried on a bomb carrier.

These bombs consist of a cylindrical metal case, with an explosive charge, and have a central tube in which are house a primer, a detonator, and a tail pistol when the depth charge is ready for use.  The depth at which the depth charge will detonate is determined by the pistol, which operates by hydrostatic pressure.  A safety device is incorporated to render the depth charge safe in the event of the carrying aircraft's sinking after a forced landing.  This safety device, however, does not always prevent detonation if the depth charge is dropped safe, as it may be affected by impact with the water.

Aircraft depth charges are thin-walled, with a loading factor of about 65 percent.  They are painted dark green overall, with a red band, painted dark green overall, with a  red band, and a colored band to indicate the nature of the explosive filling.  Attachments, comprising a nose fairing and/or a tail, are usually fitted to a depth charge to reduce the air resistance when carried externally on an aircraft, and to increase stability of the air trajectory.  Unless fitted with a parachute, failure to detonate may result if the depth charge is dropped from too great a height or at too great a speed.

DC 250lb Mk VIII (Obsolescent)

Overall length: 56 inches

Body length: 38.15 inches

Body diameter: 11 inches
 Tail length: 18 inches

Tail width: 11 inches

Total weight: 250 pounds
Charge/Weight ratio: 64%

Fuzing: Hydrostatic Tail Pistols Mks XIV, XIV*, XVI, XVI*, or Mk X**

Tail No: No.78 Mk I
  

Color and markings: Dark green overall,
1/2-inch red band near nose,
2-inch light green cross-hatched band near suspension lug.

Body Construction: The body consists of a welded cylindrical outer case to which a convex nose is welded.  The bomb is sometimes fitted with a concave nose attachment.  The rear end of the body is closed by an end cover dished inwards, which houses two filling holes that are closed by bungs.  On the cover are six equi-spaced lugs for attaching the tail.  A primer tube fits into the rear cover and extends approximately half the length of the body.  It has a 3.5-inch internal diameter, and contains the primer, pistol, and depth adjuster.


Tail Construction: The tail is an open-ended, cylindrical, sheet-metal tail supported internally by a spiral wire stiffener.  A strengthening band on the forward end carries six brackets, which are attached by studs and nuts to the six lugs on the closing cover of the depth charge.  Three equally spaced ports are provided in the tail, through one of which is passed the fuze-setting control link when the depth charge is loaded on the aircraft.  The tail breaks off on impact with the water.
 
Suspension: The bomb employs horizontal suspension by a lug welded to the body at the center of gravity.  It may be fitted with two additional lugs for suspension from US aircraft bomb racks.
  

Explosive Components:
Filling: 160lb Amatol


Remarks: This depth charge is dropped from a maximum height of 500 feet and at a maximum speed of 173 mph.

DC 250lb Mk XI and XI* (Service)

Overall length: 54.8 inches

Body length: 37 inches

Body diameter: 11 inches
 Tail length: 17.8 inches

Tail width: 11 inches

Total weight: 265 pounds
Charge/Weight ratio: 66%

Fuzing: Hydrostatic Tail Pistols Mks XIV, XVI, XIX, or Mk XX

Tail No: Mk III (Mk IV when using Pistols Mk XIX or XX)
  

Color and markings: Dark green overall,
1/2-inch red band near nose,
colored band indicating nature of explosive painted around body in front of suspension lug.

Body Construction: The body is a welded cylindrical case closed at each end by a cover which is welded on.  The central primer tube is welded into an opening in the rear cover, and extends approximately half way through the body.  Equi-spaced around the rear cover are three lugs, each drilled and tapped to receive a stud used for securing the tail to the depth charge.  Two filling holes, each closed by a bung, are provided in the rear cover.  The front cover is dished inwards to prevent ricochet.


Tail Construction: The Tail Assembly Mk III is simply a cylindrical drum open at both ends.  A strengthening ring is welded to the front end and provided with three equi-spaced brackets, weakly riveted on, which fit over the studs in the corresponding lugs on the rear end cover of the body.  The tail is strengthened by six circumferential corrugations.  The tail breaks off on impact with water.  The front of the tail has one large port for the fuze-setting control link, and two small ports to give access to pistol and valve unit when fitting the fuze-setting control link.

The Tail Mk IV is designed with arming vanes and a reach rod to arm Pistols Mks XIX and XX, which are of the air-arming type and are replacing the Tail Hydrostatic Pistols Mks XIV and XVI.  This tail is constructed with a three-segment cone, to which are riveted three fins supporting the three-segment cylindrical strut.  Three hand clearance holes are equi-spaced around the forward end of the cone.
 
Suspension: The Bomb Mk XI has a single lug welded to the case at the center of gravity for British aircraft.  The Bomb Mk XI* has dual lugs welded to its case for suspension from US aircraft.
  

Explosive Components:
Filling: 175lb Torpex






Buoyancy Bombs Introduction

Only the 250lb buoyancy bomb has been used by the British.  The bomb is designed to be dropped in front of ships under way, and to rise and detonate on contact with the ship's bottom.

The bomb consists primarily of an explosive charge, a buoyancy chamber, and a clip-on tail.  it is fuzed with a  Tail Fuze No.850.  The bomb in painted dark gray overall, and has a red nose band and a green band at the base of the ogive.





B 250lb Mk IV (Service)

Overall length: 72 inches

Body length: 42 inches

Body diameter: 14.3 inches
 Tail length: 28 inches

Tail width: 14.3 inches

Total weight: 250 pounds (approx.)
Charge/Weight ratio: 40% (approx.)

Fuzing: Tail Fuze No.850

Tail No: No.23 Mk I with the Mk III body.
  

Color and markings: Dark grey overall,
1/2-inch red band 3 inches from nose,
1/2-inch green band 9 and 1/2 inches from nose.

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 attachment can be fitted to the nose by means of three brackets, 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 forward half of the buoyancy chamber, and two circular stiffeners extend athwartships through the chamber, spot welded to the chamber wall.  An exploder tube extends centrally through the buoyancy chamber and charge case.  It is welded at the rear to the joint ring fitting inside the fuze pocket, and supported by the stiffening ring in the middle of the buoyancy chamber.


Tail Construction: The Tail No.23 Mk I, used on the Mk III body, consists of a tail cone with cylindrical strut secured by four fins riveted to the and tack welded to the tail cone.  The tail assembly is attached to the body by spring clips, and breaks free on water impact.

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 opposite ends being fastened to the support ring on the bomb base.  If these chains are tight, the fuze is armed as the contact disc rises during the arming process.  If the bomb fails to hit a ship upon rising, it sinks after a short flotation period.
 
Suspension: The bomb is suspended by a single lug secured by four screws threaded into a suspension-lug stiffener, and a boss, spot welded to the interior of the buoyancy chamber.
  

Explosive Components:
Exploders: CE exploders in central tube

Filling: 113.2lb Torpex 2, with 3.25lb TNT topping in after end of charge case.


Remarks: This bomb is designed to be dropped in front of ships under way, and to rise and detonate on contact with the ship's bottom.  The concave nose portion of this bomb is designed to give better underwater ballistics, rather than a Munroe effect.

Next Time: Incendiary, Smoke, and Light-Case (Chemical) Bombs