American Projectiles and Explosives
Explosive Bombs
Introduction
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)
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