American Projectiles and Explosives - Explosive Bombs - Modified Series, and "M" Series (Part 1)

American Projectiles and Explosives



Explosive Bombs

Introduction

Classification


Army "Modified Mark" Series: Streamlined and filled with 100% TNT.  These are now obsolete.


Army "M" Series: Parallel sides, ogival nose, and boat tail; box type tail assembly construction; and filled with 50/50 Amatol sealed at both ends with TNT surrounds.  Some are now classified as obsolescent.


Navy "Mk" Series: Similar to design of Army bombs and filled with 100% TNT; discontinued, with some exceptions, under the standardization program.


Army-Navy "AN" Series: Similar to the "M" Series, except: (1) third suspension lug added at center of gravity and 180 degrees removed from other two lugs, and (2) base plate changed to the male type.

Since the development of the "AN" series, there have been two further modifications of the general-purpose (G.P.) bombs within that series, successively the "AN-GP" and "AN-GPA1" modifications.  The changes characteristic of these two modifications are dealt with in a later post.


Practice bombs: These dummy and special signs are of great variety and have probably received more attention with the advent of peace.

Army "Modified Mark" Series

General


This particular series of bombs was not satisfactory for war use and has been abandoned, except for a few of these bombs which are used for target practice and training purposes.  They are all of the same type and are intended for the same target use, general bombardment.  The accompanying chart contains the essential data concerning the bombs of this series.

Army "M" Series

Introduction

Prior to the organization of the AN Standardization Board in 1941, these bombs were designated as "Demolition H.E." bombs; under the standardization policy they were retitled as "General Purpose High Explosive (GPHE)" bombs.


Target: Ammunition dumps, railway engines and cars, all types of construction, and aircraft on the ground.


Body Construction: These bombs may be made by any one of the following methods: (1) From seamless steel tubing in which the nose of the bomb is formed by swaging and the tail by drawing to the necessary diameter; or (2) the case may be forged in one piece; or (3) it may be formed from cast sections welded together.  These bombs have female base filling plates.


Type of suspension: Horizontally, by dual lugs.


Construction of suspension lugs: Two eyebolts welded to the body along the longitudinal axis of the bomb.  The eyebolts are formed from bar steel, shaped in the form of a U, and then welded to the body.


Color and markings: Prior to 11 March, 1942, these bombs would have been painted yellow all over, with black manufacturer's markings; since that date they have been painted olive drab with a one-inch yellow band around the nose and base and a 1/4-inch band around the center of gravity.


Material of tail: Sheet steel


Tail construction: This type of tail consists of the following parts: (1) a cast-steel sleeve secured to the body of the bomb by a fin-locking nut; (2) four fins or vanes; and (3) internal box-type struts.  One vane and one strut are pressed from one piece of metal, and the four pieces are welded to one another and to the sleeve.


Type of filling: (1) 50/50 Amatol.  Since Amatol is hygroscopic, TNT surrounds are placed around the nose and tail booster sleeve to seal the Amatol from moisture; (2) 100% TNT, which will be stencilled on the bomb.  All of this series except the 100-pound M30 contain two built in Auxiliary Boosters M104, one in the nose and one in the tail, which contain tetryl.  The 100-pound M30 has the auxiliary booster in the nose only.  The Adapter Booster M102 (tetryl) is threaded to the base plate of all bombs in the series and receives the tail fuze.

Other bombs that carry an "M" designation, although not actually classified in the "M" series, are included in this section because they are obsolescent:

Characteristics of "M" Designated A.P. Bombs

Target: Armored naval craft, reinforced concrete, heavy steel construction.

Body construction: These bombs are converted seacoast artillery shells from which the rotating bands may have been removed.  The cases are single-piece steel forgings.  The modifications of the M52 and M62 differ only slightly in external dimensions and are all equipped with a nose cap for streamlining.

Construction of tail: A truncated tail cone is secured to the bomb base by a locking nut at the top of the fuze body; four fins or vanes are supported by internal box-type struts.

Next Time: Explosive Bombs - "M" Series (Part 2)

American Projectiles and Explosives - Ground Pyrotechnics (Part 2)

American Projectiles and Explosives

Ground Pyrotechnics

Launcher Type M17A1 - M22A1; M51A1; M52A1; and M17A1B2 - M22A1B2

Length: 10.5 inches
Diameter: 1.6 inches
Delay: 6 seconds
Height of trajectory: 600 feet


Description: The signal is assembled in a cylindrical case and equipped with a finned tail assembly for stabilization purposes.  It is similar to the projector type, but modified to be fired from a service rifle or carbine.  This type has a hollow stem, which is closed by a cork plug and a wheel-shaped fin.  The "A1B2" series is the same as the "A1" series, except that the former indicates steel construction.  Special cartridges are used to ignite the propelling charge.  Embossed letters on the closing cap indicate color and type of star(s).


Operation: Remove the cork plug from the tail and place the signal on a rifle launcher.  Place the butt of the rifle on the ground as far away as practicable.   When the rifle is fired, the cartridge fires the primer, which in turn ignites the propelling charge.  The signal travels approximately 100 feet and then reverses itself and reaches an altitude of approximately 600 feet.

High-Bursting Range Signal M27A1B1

No picture available

Length: 8.37 inches
Diameter: 1.5 inches
Weight: 9.25 ounces
Height of trajectory: 700 feet


This signal has the standard tube and fin assembly as the launcher types.  It is used in training maneuvers to simulate the air burst of an artillery shell.  It produces a flash and puff of smoke, and a noise audible for at least 2,000 yards.






Flash and Sound Signal M74

No picture available

General: The Flash and Sound Signal M74 is designed for simulation of air burst of artillery fire in training troops.  It is fired from the Hand Projector M9 or the Pyrotechnic Pistol AN-M8


Description: The signal consists of an outer case, an expelling charge, and an inner cylindrical case containing the delay fuze and bursting charge.  The outer case resembles those of the aircraft double-star type.  A percussion primer in the base of the outer case extends into the expelling charge.  The expelling charge sets off the delay fuze.


Operation: When fired, the primer ignites the expelling charge.  This ignites the delay fuze and propels the inner case out of the outer case.  After a delay of about two and a half seconds, the fuze ignites the burster charge which, in exploding, produces a bright flash and a loud noise.


Remarks: With the pistol or projector at 45 degree elevation, the signal will reach a height of about 100 feet for its burst.  Helmets should be worn by exposed personnel.





Smoke Signals M62, M64, M65, and M66

Length: 10.15 inches
Diameter: 1.88 inches
Bursting altitude: 600 feet

Colors:
-M62: Red
-M64: Yellow
-M65: Green
-M66: Violet


Use: These signals are employed by artillery observes to signal or lay in a line of fire.


Description and Operation: The signal is launched in the same manner as the M17A1 series.  The fuze delay ignites an expelling charge, which expels and ignites the six smoke pellets at an altitude of 600 feet.  The pellets burn and fall, leaving a colored smoke trail.

Pistol Rocket Signals Mk1 Mod 2 and Mk 2 Mod 1

  Length: 14 inches
Diameter: 1.5 inches
Burning time: 21 seconds
Weight: 1 pound


Use: These signals are for identification on other signalling between ground troops.


Description: Similar in construction to the submarine signal, Pistol Rocket Signal Mk 1 Comet, the Pistol Rocket Signal Mk 1 Mod 2 produces a chameleon signal consisting of three parachute-borne stars which burn successively in three colors.  Each star burns for approximately seven seconds before the next color ignites.  The Pistol Rocket Signal Mk 2 Mod 1 is a smoke signal, a parachute-borne smoke candle, but is generally the same construction as the Mk 1 Mod 2.

Operation: The signals are fired from the Submarine Rocket Pistol Mk 1 Mod 0 or the Pyrotechnic Pistol AN-M8.  The primer ignites the one-gram auxiliary expelling charge, which projects the upper section of the signal to a height of 30 feet, where the rocket powder ignites, sending the signal on up to 650 feet.  There the pyrotechnic element, chameleon or smoke, ignites.  As the signal leaves the projector or pistol, the spring-loaded vanes fold out into place, stabilizing the flight of the signal.





Illuminating Hand Grenade Mk 1

  Length: 4.3 inches
Diameter: 2.1 inches
Weight: 9.2 pounds
Intensity: 60,000 candlepower
Delay: 7 seconds
Burning time: 25 seconds


Description: The grenade consists of two metal shells pressed together and sealed.  The upper shell contains a Bouchon igniter and a delay fuse.  The bottom shell contains the illuminant composition, first fire charge, ignition charge, quick match, and disc.


Operation: Pull the release pin and throw the grenade.  When the lever is released, the firing pin is freed to fire the primer.  The primer ignites the delay fuse, which burns for seven seconds and then ignites the ignition charge.  The ignition charge sets off the first fire composition, which in turn ignites the illuminant composition.  The gases from the ignition charge and first fire force the two shells apart, thus leaving the illuminant composition of the bottom shell free for burning.

Next Time: Ground Pyrotechnics (Part 3)