American Projectiles and Explosives - Explosive Bombs - "M" Series (Part 2)

American Projectiles and Explosives



Explosive Bombs

30-pound Frag. M5 (Obsolete)

No picture available

Overall length: 25.5 inches
Body length: 13.05 inches
Body diameter: 4.2 inches
Wall thickness: 0.6 inches
Tail width: 6.5 inches

Type of filling: TNT
Weight of filling: 4.66 pounds
Total weight: 29.8 pounds
Charge/weight ratio: 16.3%
Fuzing: Mk XIV

Body Construction: The body consists of a seamless steeel tube over which are fitted rings cut from cast-steel pipe.  Cast-steel nose and base pieces thread onto this center tube.


Suspension: The bombs may be suspended horizontally, vertically, or in a cluster.  U-shaped eyebolts are welded to the bomb at the center of gravity and to the rear of the tail.  Later issues of bombs were in the Cluster M3, which contained six 30-pound Frag. Bombs, M5.


Tail construction: Four rectangular sheet-steel vanes are welded to a length of one-inch cast-iron pipe that screws into the base filling plug.

2,000-pound S.A.P. M103

Overall length: 89.29 inches
Body length: 68.5 inches
Body diameter: 18.63 inches
Wall thickness: 1.3 inches
Tail length: 25.6 inches
Tail width: 25.8 inches
Tail weight: 52.7 pounds

Type of filling: Picratol
Weight of filling: 556 pounds
Total weight: 2039 pounds
Charge/weight ratio: 27%

Fuzing: Unlike smaller S.A.P. bombs, the M103 has a solid nose, permitting tail fuzing only.


Construction: The body of the M103 is fabricated from seamless steel tubing, somewhat streamlined in shape and with a semi-pointed nose.  No provision is made for nose fuzing in this bomb.  Suspension lugs are welded tot he case in a manner similar to the G.P. bombs.  Trunnions on a band may be fitted for dive-bombing.  A box-type tail is employed as on the G.P. bombs.


Filling: Picratol, a mixture of 52% Explosive "D" and 48% TNT, is poured as the main charge, with a wax pad in the nose to cushion the explosive against premature detonation on impact with a hard target.


Remarks: The suspension lugs are 30 inches apart.  Suspension bands are under development and will be issued, when available, for installations requiring 14-inch suspension.

4-pound Frag. "Butterfly" M83

Overall length: 3 inches
Body length: 3 inches
Body diameter: 3.1 inches
Wall thickness: 0.25 inches

Type of filling: TNT
Weight of filling: 0.47 pounds
Total weight: 3.2 pounds
Charge/weight ratio: 15%

Fuzing: M129 Air or Ground burst, M130 Time, maximum 30 minutes, or M131 Anti-Disturbance.

Body Construction: The bomb body is cylindrical in shape, cast in two halves and welded together.  The fuze cavity is situated athwart-ships in the body, is 1 and 3/4 inches in diameter, and is threaded with a left-hand thread.  The left-hand thread is to prevent unscrewing of the fuze while the bomb is in flight.


Arming vane assembly: The vane assembly consists of four pieces hinged together - two semi-cylindrical surfaces (wings) and two discs (propeller blades) inclined at a slight angle.  While the bomb is still in the cluster, the vane assembly is folded around the bomb to form a cylindrical casing which can be closed against the pressure of the vane coil springs by means of a safety clip.  The arming spindle projects through the bomb casing.

When the bombs are packed in the cluster adapter, the safety clips are removed by the bombs remain in their closed status because of their proximity to each other.  When the cluster adapter bursts open, the bombs scatter and the vane assembly on each bomb is spread open by the force of its coil springs.  The vane assembly is forced by air resistance to the top of the arming spindle, where the square head on the spindle engages the square hole in the assembly.  The two wings reduce the velocity of descent of the bomb.  The two propellers, being set at angles to each other, case the vane assembly to turn in a counterclockwise direction, thereby screwing the arming spindle out of the fuze body and permitting the fuze to arm.  The arming spindle is not completely withdrawn from the fuze, being retained in the fuze by a collar on the spindle.


Markings: The bombs are painted olive drab, with a half-inch yellow band running horizontally around the folded wings.

90-pound Frag. M82

Overall length: 28 inches
Body length: 19.8 inches
Body diameter: 6 inches
Wall thickness: 0.94 inches
Tail length: 9.3 inches
Tail width: 8.1 inches
Tail weight: 2.8 inches

Type of filling: Composition B
Weight of filling: 12 pounds
Total weight: 91.6 pounds
Charge/weight ratio: 13.1%

Construction: Nose and tail pieces of cast steel screw onto a central section of seamless steel tubing.  A square helical steel spring is wound around the steel tubing.  The nose and tail pieces are partially cut through, to afford greater fragmentation.  The bomb is suspended by single lug or in a cluster (M27) of six bombs.  The tail is of normal U.S. box construction and is secured to the bomb by a locking ring.

120-pound Para-Frag. M86

Parachute container length: 35.5 inches
Diameter: 6.5 inches


Description: The M86 consists of the 90-pound Fragmentation Bomb M82, and a Parachute Unit M5 which is screwed to the base of the bomb body in place of the normal tail fin assembly.  Both units are issued separately and must be assembled prior to use.

The Parachute Unit M5 consists of a cylindrical container housing the parachute.  The lid of the container is fastened by a latch, which is secured by the arming wire.

The bomb is fuzed with the Fuze AN-M120 or AN-M120A1 by using the Adapter Booster M117.

Suspension: The bomb can be used ina  bomb station having the clearance of a 500-pound bomb, and may be suspended singly or as a two-bomb cluster with the Cluster Adapter M12.  One suspension lug is welded to the bomb at the center of gravity, and two suspension bands are issued with the parachute unit.  The larger-diameter band is secured on the parachute unit to be used in conjunction with the suspension lug or the smaller-diameter band secured on the bomb body.


Operation: Thea arming wire, which is fastened to the bomb shackle, passes through the lug of the rear suspension band and the latch on the parachute container, but not through the fuze.  This secures the latch and prevents the parachute from opening until immediately after release of the bomb.  The arming wire which passes through the fuze is fastened to the parachute by the arming cord.

On release, the arming wire is withdrawn from the latch on the container.  As the bomb falls, the air stream removes the lid from the container and allows the parachute to open.  The arming cord is attached ot the shroud line and is pulled as the parachute opens, thereby permitting the fuze to arm.

Fragmentation Bomb Clusters

M1 - Adapter M1

100-pound size for six 20-pound Frag. Bombs AN-M41.  It is 46.75 inches long and weighs 125 pounds.  It has lugs for double-hook suspension only.  The release mechanism operates by means of a cartridge and firing mechanism.



M27 - Adapter M14

500-pound size cluster for six 90-pound Frag. Bombs M82.  The adapter consists of two longitudinal steel tubes, 56 inches long, to which are welded four steel plates forming the support for the six bombs.  The lower tube serves as the backbone of the cluster; and the upper tube carries the suspension lugs, the buckles for the releasing straps, and the adapters for the nose and tail fuzes.  The Nose Fuze M111A2 or M155 is used; however, there is no mechanical time fuze in the tail.

The cluster may be adjusted to release the bombs immediately or, through the use of mechanical time fuzes, to discharge the bombs 5 to 92 seconds after the release of the cluster from the plane.  If it is intended that the cluster is to open immediately, the shear wire is cut after the arming wire is installed, and no fuze is used.  The immediate opening of the cluster produces the most favorable impact pattern.  The cluster must open at a minimum altitude of 1,000 feet in order that the bomb fuze may arm.

M28 - Adapter M15A1

100-pound size for twenty-four 4-pound Frag. Bombs M83.  It is a cylindrical sheet-metal case, which opens longitudinally, being hinged at the rear and closed by a nose cup.  It is 47.35 inches long and 8 inches in diameter, and weighs 155 pounds loaded.  It uses Fuze M155 or AN-M146.

These clusters are released from altitudes of not less than 3,000 feet and not more than 5,000 feet.  Fuze settings for function after release are varied from five seconds at minimum release altitude to eight seconds at maximum release altitude.  When the fuze fires, it releases the nose closing cup, allowing the adapter to open and release the bombs.  The bombs scatter to form a pattern over an area of approximately 300 by 200 feet.

M28A1 - Adapter M15A1

The Cluster M28A1 is the same as the M28, except that it incorporates a spoiler ring around the nose and a drag plate secured ot the tail by four screws.  These two devices were added because the dropping altitude for the M28 was limited by the high velocity attained by the clusters at high altitudes, resulting in damage to the butterfly when the cluster opened.  When drag plates and spoiler rings are used, the recommended release altitude is 1,500 feet with a six-second fuze setting, or any high altitude which will open the cluster at a height between 1,000 to 2,5000 feet.

M28A2 - Adapter M15A2

This A2 modification has a new locking cup, which is secured to the adapter by two slotted screws.  Otherwise, it is the same.

M29 - Adapter M16A1

500-pound size for 90 4-pound Frag. Bombs M83.  The container is like the M15, except for size.  In the Adapter M16, the bombs are loaded in "wafer" assemblies.  This cluster has a third single lug for British suspension.

M29A1 - Adapter M16A2

This A1 modification has the new locking cap, secured to the adapter by two slotted screws.  Otherwise, it is the same.

Remarks

For Navy usage, the Bureau of Ordnance recommends that the case-locking bushing it has developed be used with all "Butterfly" fragmentation clusters, including the M28, M28A1, M28A2, M29, and M29A1.  One end of the bushing screws into the fuze adapter, and the other end is threaded internally to receive the fuze.  The locking cup is retained positively by a safety wire which passes through a hole in the locking-cup tab and around a cotter pin placed int he bushing.  When the fuze fires, the locking cup is blown into the cluster, shearing the loops of safety wire and allowing the adapter to open.

Next Time: Navy "MK" Series (Part 1)

British Explosive Ordnance - Obsolete Bombs

British Explosive Ordnance

Obsolete Bombs Introduction


The various bombs of different types included in this section have all been declared obsolete, but because of the possibility that they still may be encountered, it is deemed desirable to give complete information regarding them.

Older obsolete bombs, included only as a matter of interest, are listed in chart form at the end of the chapter.









AT 9lb, Mk I  (Obsolete)

Overall length: 14 inches
Maximum body diameter: 4 and 1/2 inches squared

Total weight: 8.5 pounds
Charge/weight ratio: 80%

Fuzing: Tail Fuze No.847
  

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

  

Body Construction: The body is made of thin metal, approximately rectangular in shape, having a square cross section with rounded corners.  It tapers slightly from the rear toward the nose.  The body is closed at the nose end by a front cover housing a nose cup, which is taped and cemented in place.  The nose cup of the rear bomb forms a safety device for the fuze in the front bomb of a pair, as bombs are dropped in pairs.  The rear cover is located approximately in the middle of the bomb.  The bomb incorporates a steel, cone-shaped charge.


Tail Construction: The tail is integral with the body, being only a continuation of the thin metal case.  The rear bomb of a pair has a retarder plate to pull the rear bomb free of the front one when dropped from the container.  The tail also has a safety tube of light-gauge metal with a  cardboard inner sleeve, forming a safety device for the fuze of the rear bomb of a pair.  A locating plate near the rear of the safety tube locates the tube in the tail of the bomb.

 
Suspension: These bombs are carried in the 250lb Small Bomb Container, which holds 24 bombs.  They are loaded in pairs, with the nose of the rear bomb houses in the tail of the front bomb.


Filling:
-Exploder: CE pellet housed in the bottom of the exploder container
-Filling: Nobel's explosive No.808, with shaped charge effect.


Remarks: The bomb is designed for use against tanks and armored vehicles.  It will blow a hole approximately nine inches in diameter in armor plating 2 inches thick, and is effecting at striking angles up to 45 degrees.

The 9lb AT Practice Bomb Mk I is approximately the same shape, size, and filled weight, and has the same approximate ballistic characteristics.  However, it has neither exploder nor detonator.  Its body breaks up on impact with the target to release a white filling, clearly visible from the air.

HE 20lb Mk I (Obsolete)

   

Overall length: 25 inches
Body length (w/o tail adapter): 11 inches (approx.)
Body diameter: 5.175 inches
Tail length (w/ tail adapter): 12 inches (approx.)
Tail width: 6 inches (approx.)

Total weight: 27 pounds (approx.)
Charge/weight ratio: 20% (approx.)

Fuzing: Nose Pistol No.16
  

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

  

Body Construction: The bomb has a steel, semi-steel or malleable-iron body, hollow and open at both ends, with the forward end threaded internally to receive the nose adapter, and the after end internally threaded to take the tail adapter.  The nose adapter has three different-sized threads, to take the detonator-holder and the exploder container from the rear,a nd the pistol from the front.  The flange of the nose adapter is externally threaded to receive a screw-on pistol cover.  The tail adapter is tapered to conform to the rearward streamlining of the body, with a central bore threaded to receive the tail rod.


Tail Construction: The bomb has a wooden tail cone, conforming to the streamlined shape of the body.  Two diametrical saw-cuts at right angles extend from the after end, over a slightly greater length than that of the tail vanes, to accommodate the four sheet-metal tail vanes, which are made in integral pairs.  The tail cone is bored axially to take the tail rod, and fits into the cavity in the tail adapter.


Suspension: A wrought-iron or mild steel suspension lug is riveted to the bomb body.


Filling:
-Exploder: 3 sold and 1 perforate CE pellets.
-Filling: 5 pounds (approx.) TNT


Remarks: This bomb was intended for attacking personnel, air strips, and road transports.

RL 112lb Mks V, VI, and VIII (Obsolete)
   

   

Overall length: 18 inches
Body diameter: 8 inches
Wall thickness: Solid body

Total weight: 10 pounds

Fuzing: Nose Pistol No. 8 Mk I, or Nose Pistol No.19 Mks I and II; Tail Pistol No.5B Mks I and II
  

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

  

Body Construction: The body of these bombs is a single streamlined casting, steel for Mks V and VII and iron for Mk VI, threaded at the nose and tail to take adapters for the central exploder tube.


Tail Construction:
Mk V: The tail of the Bomb Mk V consists of four tail fins, which fit over the body and are fastened in place with screws.  Two sets of box-type struts reinforce the tail fins.


Mks VI and VII: The tail assembly of the Bombs Mk VI and Mk VII consists of a tail cone, which slides over the after end of the bomb body and sis secured by a locknut on the exploder tube.  Four tail fins are riveted on the cone and are held in place by two sets of box-type struts.


Suspension: The Bomb Mk V has a U-shaped eye-bolt secured to the body with screws at the center of gravity.

The Bombs Mk VI and Mk VII have a U-shaped eye-bolt fastened to a suspension band around the center of gravity.


Filling:
-Exploder: TNT and CE pellets
-Filling: Amatol 80/20, or TNT
  

GP 120lb Mks I and II (Obsolete)
     

Overall length: 42.4 inches
Body length: 21.5 inches
Body diameter: 8.1 inches
Wall thickness: 0.5 inches
Tail length: 15.7 inches
Tail width: 8 inches

Total weight: 120 pounds (Amatol 80/20)
Charge/weight ratio: 25%

Fuzing: Nose Pistol No.19; Tail Pistol No.21
  

Color and markings:  Yellow overall,
1/2-inch red band around nose and 1 inch light green band around body,
longitudinal green bar on body and tail indicates explodering scheme..

  

Body Construction: The body is a streamlined steel casting or forging, threaded at the nose to take the nose adapter, which holds the central exploder tube.  At the other end of the casting is a threaded base plug through which the exploder tube passes.  Welded to the end of the casting is a streamlined section of thin metal, containing no explosive, which is tapered to take the tail ring.  The exploder passes through this section also.


Tail Construction: A truncated cone fits over the rear section of body and is held to it by a locknut over the exploder tube.  Three mild-steel fins are fastened to the cone, and are reinforced by a cylindrical strut.


Suspension: The bomb uses a single suspension lug secured to the body by four screws.


Filling:
-Exploder: TNT and CE pellets
-Filling: 36.5 pounds TNT, or 30 pounds Amatol 80/20

 

GP 500lb Mks I, II and III (Obsolete)
     

Overall length: 68.7 inches
Body length: 35.7 inches
Body diameter: 13 inches
Wall thickness: 7/8 inches
Tail width: 13 inches

Total weight: 509 pounds (TNT)
Charge/weight ratio: 28%

Fuzing: Nose Pistol No.19; Tail Pistol No.17 or 22
Tail No.: No.1 Mk I (Mk III bomb only)
  

Color and markings:  Yellow overall,
1/2-inch red band around nose and 1 inch light green band around body,
light green bar on body and tail indicates explodering scheme..

  

Body Construction: The body is a streamlined steel casting or forging threaded at the nose to take the nose adapter, which holds the central exploder tube.  At the opposite end is a threaded base plug through which the exploder tube passes.  Welded to the after end of the body is a streamlined cone of thin metal, containing no explosive, which is tapered to take the tail ring.  The exploder also passes through this section.


Tail Construction: The tail has a truncated cone, which fits over the rear section of the body and is held to it by a locknut over the exploder tube.  Four mild-steel fins are fastened to the cone, and are reinforced by a cylindrical strut.


Suspension: The bomb is suspended by a single suspension lug secured to the body by four screws.


Filling:
-Exploder: TNT and CE pellets
-Filling: 143 pounds TNT, or 134 pounds Amatol 80/20

Remarks: The tail fins are usually painted red when time pistols are used.

HC 2000lb Mk I (Obsolete)

   
Overall length: 162 inches

Body length: 99.5 inches

Body diameter: 18.5 inches
Wall thickness: 0.19 inches
Tail length: 60 inches
Tail width: 18.6 inches

Total weight: 1842 pounds
Charge/Weight ratio: 73%

Fuzing: Nose Pistol No.27, 42, or 44
Tail No.: No.32 Mk I, or No.10 Mk I or II, or Parachute Attachment
  

Color and markings: Dark green overall,
1/2-inch red band 3 and 1/2 inches from front edge of cylindrical shell,
2-inch light green band 16 inches from edge.

Body Construction: The body consists of a cylindrical steel shell with a hollow, conical nose piece welded to one end, parallel sides, and a closing plate bolted to an angle ring which is welded in position a short distance within the other end.  A radial strengthening band is welded internally at the center of gravity, and its ends are welded to a steel block.  Holes tapped through the shell and steel block receive the suspension lug screws.  Side pockets for supplementary fuzing are present near the base end, but are not used.  The shell is strengthened longitudinally by two channel beams welded to each end of a central steel block and to the shell interior.


Tail Construction: The Tail No.32 Mk I assembly consists of a cylinder of light-gauge metal with a metal tray secured in its forward end and a strengthening ring in its open rear end.  The tray has a series of equispaced bayonet dogs for attaching to the body bayonet joints welded to it.  The cylinder has a number of openings to give it stability.

The parachute attachment has a parachute 5 feet, 6 inches in diameter, attached to a metal tray having bayonet dogs for attaching it to the body.  The parachute is retained by waterproofed fabric and a retaining pin.  The retaining pin is attached to a static cord stitched on the outside of the last protective panel, and connected to the bomb carrier or aircraft.  On release the cord pulls the retaining pin and chute free, and breaks off from the plane when the chute is extended.
 

Suspension: The bomb is suspended by a single suspension lug bolted to the body and an internal steel block at the center of gravity.  The screw holes are closed by transit screws until the bomb is to be used, at which time the lug is attached.
  

Explosive Components:
Exploders: A central exploder tube extends from the nose exploder container.  The tube contains eight 33 and 1/4 ounce TNT exploders.  The exploder container contains a 9 ounce TNT exploder.

Filling: 1340lb Amatol 60/40 sealed at each end with an approved composition


Remarks: This bomb may be fitted with a nose attachment of light-gauge metal to retard the bomb in flight.  It consists of a cylinder fitting over the forward end of the body shell and projecting forward beyond it around the conical nose piece.  Two side fuzing pockets are usually not used, but might contain the Time Pistol No.47.

 

AS 35lb Mks I and II (Obsolete)

Overall length: 29.2 inches

Body length: 17.2 inches

Body diameter: 7 inches
Wall thickness: 0.064 inches
Tail length: 17 inches (approx.)
Tail width: 7 inches

Total weight: 35 pounds
Charge/Weight ratio: 46%

Fuzing: Nose Fuze No.866
  

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

Body Construction: The bomb has parallel sides, with a nose adapter and a tapered rear section.  A tail adapter secures the tail to the body.  The explosive charge is cone shaped, employing the principle of Munroe shaped charge.  A cylindrical nose attachment is welded onto the nose adapter by four tack welds.  The exploder is in the rear of the body, and is initiated by a flash from the nose fuze, communicated through the supporting tube extending from the nose cavity to the exploder.


Tail Construction: The tail consists of a long hollow tube with a cylindrical strut attached to it by six fins.  The tail threads into the tail adapter, and is secured by a locking screw.  The six fins are formed by three sets of W-shaped supports welded to the tail tube.
 
Suspension: The Bomb Mk I has a single lug for suspension in aircraft.  The Mk II has no lug, as it is intended to be fired from shipboard.
  

Explosive Components:
Exploder: CE pellets
Filling: 16lb RDX/TNT 60/40.  The after end is sealed by a 1/4-inch topping of TNT.

Remarks: The Bomb Mk I was designed for use by Coastal Command and was intended to be dropped from aircraft.  The Bomb Mk II has no suspension lug, and is intended for spigot projection from ships.



 






DC 450lb Mk VII (Obsolete)

Overall length: 67.25 inches
Body length: 27.75 inches

Body diameter: 17.5 inches
Tail length: 32 inches (approx.)
Tail width: 17.5 inches

Total weight: 450 pounds
Charge/weight ratio: 64%

Fuzing: Mk X** pistol and depth adjuster
  

Color and markings: Dark green overall with circumferential red and green bands

Body Construction: The body consists of a welded cylindrical case, closed by two covers connected by a central tube called the primer tube.  This tube, housing the primer, pistol, and depth adjuster, has an internal diameter of 3.5 inches.  Three lifting eyes with rings are provided, one on the cover at the primer end, and two on the cover at the opposite end.  The cover at the primer end has two filling holes which are closed by bungs.  It may or may not have a nose attachment and tail.  The bomb is carried on aircraft with the primer end forward, except when fitted with the parachute attachment, in which case the pistol and depth adjuster are forward.


Nose Attachment: The bomb may use a hemispherical hollow nose held on by the side straps, which also secure the tail assembly.


Tail Construction: The tail, when fitted, consists of a cylindrical strut attached to a hollow tail cone by four fins.  Three brackets, equispaced around the cone, are fitted to take the ends of the straps which secure the nose and tail attachments, both of which break off on impact with water.  The bomb may have a parachute attachment on the primer end if dropped from high-speed aircraft.

 
Suspension: The bomb is suspended by a single lug on a suspension band around the center of gravity.


Explosive Components:
Filling: 290lb Amatol

IB 25lb Mks I and II (Obsolete)

Overall length: 32.6 inches
Body diameter: 5.03 inches

Tail length: 13.55 inches

Total weight: 25 pounds

Fuzing: Simple impact striker
  

Color and markings: Dull red overall,
two 1/2-inch black bands separated by 1/2-inch red band painted around the nose.

Description: The Bomb Mk I consists of a cylindrical steel tube secured to a hollow, sharp-pointed nose by a nose adapter (built up externally to streamlined form by a cardboard fairing), a column of seven closed containers, termed fire-pots, accommodated in the body tube, a flanged base adapter which affords a mounting for a cap holder, a tail cone with a cylindrical tail vane secured to it by four vane supports, and a tail tube which accommodates a striker pellet, with a shear wire and creep spring, and a safety rod.

Each of the seven fire-pots consists of a cylindrical container made of magnesium alloy and formed with a central tube, which communicates, through a fire hole, with a recess in a central boss on the base of the container.  The container is closed by a magnesium alloy lid, which has a shallow central recess in its outer side.  Holes through he lid place this recess in communication with the interior of the container.  The ignition cap contains a layer of gunpowder and a layer of detonating composition.

The central tube of each of the fire-pots houses a delay charge and is surrounded by a delay charge and a priming charge for the thermite and magnesium filling, which occupies the remainder of the annular chamber in the fire-pot.  A loop of quickmatch extends into the bore of the central tube and has its two ends carried out through the slots in the tube and through two of the holes in the lid.  An ejection charge of gunpowder is retained in the recess in a central boss of each fire-pot by a paper disc, which is secured in position by shellac.

The tail cone fits over the flange of the base adapter and is held assembled to the bomb body by a tail nut, which screws onto the rear end of the tail tube against a tail adapter.  The tail adapter fits into the rear end of the tail cone.

The striker pellet has a sharp point at the forward end and is held in the safe position by a shear wire passed through holes in the striker pellet and tail tube.  The ends of the shear wire are soldered to prevent removal.  The rear end of the striker pellet receives the forward threaded end of the safety rod.  The creep spring is house in the forward end of the tail tube and bears against the cap holder and the striker pellet.  The safety rod passes through the tail tube and is screwed into the threaded bore of the striker pellet.

The Bomb Mk II has only a slight difference in the tail plate.


Parachute Attachment: Either a Parachute Attachment No.1 Mk I or a No.1 Mk II may be used with this bomb.  The Attachment No.1 Mk I consists of a small parachute housed in a container of sheet metal, consisting of a cylindrical housing plate and a cover.  It fits loosely in the cylindrical strut of the bomb tail.  The chute is 15 inches in diameter and vented at the peak.  The Attachment No.1 Mk II is similar, except that it is housed in a collapsible cardboard container between cardboard packing discs.


Striker Attachment: There are two striker attachments, the No.1 Mk I, and the No.1 Mk II.  No.1 Mk I consists of a coupling fork, snatch rod, striker rod, coupling socket, and a retaining sleeve, which houses a spring.  The No.1 Mk II is similar, except that the coupling fork is fitted with a quick-release pin.


Functioning: Whent he bomb using the Parachute and Striker Attachments No.1 Mk I is released, the cover pulls the chute out.  The chute opens and pulls the snatch rod against the action of the spring until the striker rod retaining balls escape into the annular recess in the retaining sleeve.  The striker rod then moves down against the striker pellet.  On impact, the inertia of the rod and pellet combine to shear the shear wire, overcome the creep spring, and pierce the ignition cap, igniting the blowing charge and blowing the base adapter and complete tail and parachute assembly from the body tube.  The quickmatch, which passes through the lid and into the central tube of the rearmost magnesium alloy fire-pot, is also ignited, and, in turn, the quickmatch ignites the delay charges in and around the central tube of the fire-pot.

While the central tube delay charge is burning through, the outer delay charge initiates the surrounding priming charge, which, in turn, ignites the incendiary composition around it.  Meanwhile, the central delay charge burns through and fires the ejection charge in the base of the fire-pot.  This has the effect of ejecting the activated fire-pot from the bomb and also igniting the quickmatch of the second fire-pot, etc.  Each ejected fire-pot will continue to burn for approximately 10 minutes; the magnesium alloy container and lid being consumed.

Finally, the quickmatch in the lod closing the nose of the bomb is ignited by the last ejection charge and initiates the priming charge, which, in turn, ignites the incendiary composition of the nose, and provides an additional fire source.

When used with the Parachute and Striker Attachment No.1 Mk II, the parachute is blown out of the cylindrical shroud on the tail and the chute opens, freeing the striker mechanism.  Functioning after this is the same as that with Attachments No.1 Mk I.

Suspension: The bombs may be carried in a Small Bomb Container, or from a bomb carrier by a lug on a suspension band.


Explosive Components:
Filling: 1lb Thermite, and 5lb, 4oz Magnesium

IB 250lb Mks I and II (Obsolete)



Overall length (w/o fuze): 61 inches (approx.)
Body length: 34.1 inches

Body diameter: 12 inches
Tail length: 27.2 inches
Tail width: 11.7 inches
Fuel weight: 68 pounds

Total weight: 193 pounds

Fuzing: Nose Fuze No.36 Mk II with Ejector Charge No.2 Mk I
Tail No.: No.1 Mk I
  

Color and markings: Red overall,
two 2-inch black bands separated by a 2-inch bright red band near nose.

Description: The bomb has a cylindrical body with a hemispherical nose and parallel sides.  An ejector-charge container is screwed and cemented into the nose and takes the nose fuze.  The tail consists of a tail cone and a cylindrical strut attached to the cone by four fins.  The after end of the body is closed by a tail plate, which is lightly secured to the body.


Functioning: On impact, the fuze functions and ignites the gunpowder ejection charge, which in turn ignites the incendiary filling and ejects it with the tail and tail plate.


Suspension: The bomb is suspended by a single suspension lug.


Filling: The Bomb Mk I is filled with a phosphorus-rubber-benzene mixture.  The Bomb Mk II is filled with a "sticky flammable liquid."  The ejector charge consists of black powder.

Remarks: This bomb was intended primarily for attacking forested areas, and can be dropped from heights up to 8,000 feet.

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