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)