COMMON CHARACTERISTICS OF "AN" DESIGNATED GENERAL PURPOSE BOMBS:

Body Construction:

The body construction of American G.P. bombs may be in one, two, or three pieces. Methods of manufacture include (a) one piece cast or spun, (b) two piece cast or wel-ded or (c) three piece cast and welded. The ogival nose tapers to join the thin parallel side walls which terminate in a boat tailed shape at the after end. The threaded nose opening is closed by the fuze seat liner and the threaded base opening is closed by a male plug, the tail fuze pocket being made by the adapter booster.

Suspension

Dual suspension lugs for horizontal suspension are welded directly to the bomb case, being spaced 14 inches apart on bombs up to 2000 pounds, and 30 inches apart on bombs 2000 pounds and over. A single horizontal suspension lug is also welded to the bomb case at the center of gravity and diametrically opposite the dual lugs. The lugs are eye-bolts, shaped from bar steel and formed in the shape of a U. M series bombs could be carried on single suspension racks by using an additional single suspension lug welded on a band fitting around the bomb body at the center of gravity.

For suspension in dive bomb displacement gear, trunnions are provided on a separate band which may be one of two types. The first type provides the trunnion only, and the second, a more common type, provides a single hoisting lug in addition to the trunnions. On some of the newer designs of AN bombs of Navy manufacture, the suspension and hoisting fittings are not attached to the bomb case by welding, but are held to the case by threaded bolts fitting into holes tapped and threaded into the body. For suspension in torpedo slings, the torpedo sling guide key found on Navy bombs can be made on AN bombs by using the base of the single suspension lug with the lug removed by gentle hacksawing.

To hoist bombs into Navy planes, the AN bombs not equipped with hoisting lugs must have a hoisting lug furnished by either an expandable band with single or dual lugs, or by a removable hoisting band. The removable band is preferred, since it does not affect the terminal velocity of the bomb. The newest and best of these bands is the Mark 8 univer-sal hoisting band. For Army planes, bombs are usually hoisted by canvas slings, which also have the advantage of not effecting air trajectory.

Tail Fin Construction

The tail construction is known as the box type tail and consists of the following parts: A cast steel sleeve secured to the bods of the bomb by a fin locking nut, four sheet steel fins supported by 4 sheet steel struts in the shape of a box. One fin and one strut are pressed from the single piece of metal and the four piece are then welded to the sleeve. 'A' indicates heavier construction for high altitude bombing.

Color and Markings

The standard color scheme employed in these bombs since March 11, 1942, has been an olive drab body with yellow bands to indicate the H.E. filler. The banding system for Amatol and TNT fillers is a 1" yellow band at the nose, a 1" yellow band at the tail of the bomb body, and a 1/4" dotted band at the center of gravity. Because Composition "B" is more sensitive and requires more careful handling, it is given an additional marking of a second 1" yellow band at the nose and at the tail. On these bands "Comp. B" is stencilled in black paint. Recent production eliminates the 1/4" band, since the center of gravity is located accurately enough by the single suspension lug.

The following standard markings are painted on the bomb body in black paint; type, weight and name of the bomb, type filling, lot number, place of filling and date of filling and ispector's initials.

Additional indestructable marking is stamped into the metal of the bomb case on the rear conical surface of the bomb body; type size, name, marker's initiales, lot number and date (i.e. G.P. 500 lb. AN-M64 CSCO Lot 57 4/42).

Explosve Filling

The filling of these bombs is accomplished in the followings manner. With the nose fuze seat liner in place, the bomb is placed in end nose down and an M104 auxiliary booster is positioned behind it. The M104 is a bakelite tube containing tetryl pellets. The initial pour of the explosive is sufficient to secure the auxiliary booster when it cools, then the remainder of the filling, 50/50 Amatol, TNT or Composition "B" is added until ap-proximately 6 inches remains to be filled. A second M104 auxiliary booster is then insert-ed in all bombs except the 100 lb. and the tail surround is added to complete the filling. A wooden former is inserted in the tail fuze cavity as the filling cools. After cooling, the former is removed and the appropiate adapter booster is inserted. The adapter booster consists of the fuze seat liner with an additional steel cup containing a tetryl pellet. The M102 (and M102A1) adapter booster has an internal thread diameter of 1.50 inches. The M115 adapter booster has an internal thread diameter of 2.0 inches, and an adapter ring to further reduce the diameter to 1.50 inches when smaller fuzes are used. For reference to adapter booster, see page 145.

In except production the auxiliary booster has been eliminated in Composition "B" load-ed AN-M64 500 lb., AN-M65 1000 lb., and AN-M66 2000 lb. G.P. bombs. It has been found that the auxiliary booster has little connection with the effectiveness of the bomb, considering the fact that Comp. "B"'s rate of detonation is 500 ft/sec greater than the tetryl in the booster.