American Projectiles and Explosives
Practice Bombs
Navy Practice Bombs
Miniature 3-pound Mk 3, Mk 4, AN-Mk 5, AN-Mk 23; and 4.5-pound AN-Mk 43
Overall length: 8.25 inches
Color: Unpainted
These small, cast-alloy bombs have a tube along their longitudinal axis which houses the Signal Cartridge AN-Mk 4 or Mk 5, a pyrotechnic charge for spotting purposes. The differences between these bombs are matters of size. The Miniature Practice Bomb AN-Mk 43 weighs 4.5 pounds; the others of this series weigh 3 pounds.
Miniature 13-pound Mk 19 or Mk 19 Mod 1
This bomb is like the other miniatures, except that it is larger. Its length is 13 inches, while its weight is 13 pounds.
"Old" Series Practice Bombs (Obsolete or being replaced)
No fuzes are used in these bombs, and they contain no spotting charge, being filled either with water or with wet sand. The filling is usually stenciled on the body of the bomb. To prevent freezing and splitting of cases at high altitudes, anti-freeze is added. To improve spotting of hits, a spotting dye is also used.
"New" Series Practice Bombs
Mk 15 Mod 3 uses Spotting Signal Mk 7; the others use Mk 6 Mod 0.
This series bomb is a welded sheet-steel light-case design having identical dimensions to AN standard G.P. bombs, and uses AN standard G.P. bomb tails. The bomb has, welded to its body, two suspension lugs spaced 14 inches apart. Seven threaded recesses, located on the periphery at the approximate center of gravity, are for various hoisting conditions. At 90 degrees, on each side of the suspension lugs and slightly before the hoisting recesses, are threaded opening to receive trunnions.
By means of a strap, the appropriate practice bomb signal, Mk 6 or Mk 7, may be attached to the tail assembly with the forward end of the signal seated in a recess in the after end of the bomb body.
A flat-nose attachment has been designed for use with the Practice Bomb Mk 15 Mod 3 for anti-submarine bombing practice. The flat nose is installed by removing the nose-filling cap, slipping the attachment over the nose of the bomb, and then screwing the filling cap down tightly by hand to hold the attachment in place. The flat nose will prevent ricochet at entrance angles as low as 9 degrees.
The 2,000-pound size container was designed for an incendiary or practice filler but, thus far, it is approved by the Bureau of Ordnance for practice filling, sand, only. As designed for incendiary loads, it would take a nose fuze, the Burster Mk 1, and the Igniter Mk 40; however this is subject to change before Bureau approval of the bomb as an incendiary. The Mk 67 has standard suspension lugs and provision for trunnions.
Practice Bomb Signals (Navy)
Miniature 13-pound Mk 19 or Mk 19 Mod 1
This bomb is like the other miniatures, except that it is larger. Its length is 13 inches, while its weight is 13 pounds.
"Old" Series Practice Bombs (Obsolete or being replaced)
No fuzes are used in these bombs, and they contain no spotting charge, being filled either with water or with wet sand. The filling is usually stenciled on the body of the bomb. To prevent freezing and splitting of cases at high altitudes, anti-freeze is added. To improve spotting of hits, a spotting dye is also used.
"New" Series Practice Bombs
Mk 15 Mod 3 uses Spotting Signal Mk 7; the others use Mk 6 Mod 0.
This series bomb is a welded sheet-steel light-case design having identical dimensions to AN standard G.P. bombs, and uses AN standard G.P. bomb tails. The bomb has, welded to its body, two suspension lugs spaced 14 inches apart. Seven threaded recesses, located on the periphery at the approximate center of gravity, are for various hoisting conditions. At 90 degrees, on each side of the suspension lugs and slightly before the hoisting recesses, are threaded opening to receive trunnions.
By means of a strap, the appropriate practice bomb signal, Mk 6 or Mk 7, may be attached to the tail assembly with the forward end of the signal seated in a recess in the after end of the bomb body.
A flat-nose attachment has been designed for use with the Practice Bomb Mk 15 Mod 3 for anti-submarine bombing practice. The flat nose is installed by removing the nose-filling cap, slipping the attachment over the nose of the bomb, and then screwing the filling cap down tightly by hand to hold the attachment in place. The flat nose will prevent ricochet at entrance angles as low as 9 degrees.
The 2,000-pound size container was designed for an incendiary or practice filler but, thus far, it is approved by the Bureau of Ordnance for practice filling, sand, only. As designed for incendiary loads, it would take a nose fuze, the Burster Mk 1, and the Igniter Mk 40; however this is subject to change before Bureau approval of the bomb as an incendiary. The Mk 67 has standard suspension lugs and provision for trunnions.
Practice Bomb Signals (Navy)
AN-Mk 4 and AN-Mk 5: For the miniature practice bombs, these signals allow observers to spot the impact of salvos. The Practice Signal Cartridge AN-Mk 4 is an extra long 10-gauge shotgun shell which is inserted in the nose of the bomb. On impact, the cartridge is fired, expelling a large puff of black smoke from the tail of the bomb. The firing device consists of two shallow cups separated by a spacer, the firing pin extending through the bottom of one cup. The Signal Cartridge Mk 5 is the same size but filled with fluorescein, which stains the water, giving a spot of longer duration than the AN-Mk 4.
Mk 6 Mod and Mk 7 Mod 0: These signals are essentially cans of black powder fitted with the Fuze Mk 247. The Mk 6 is used in the Practice Bombs Mk 65 and Mk 66; the Mk 7 in the Bomb Mk 15 Mod 3. They are attached to the rear of teh bomb by brackets or a strap arrangement. The Signal Mk 7 is 13.08 inches long and 2 inches in diameter. It has a total weight of 2.5 pounds. It has a filling of one pound of black powder. The Mk 6 is generally the same, except that the fuze is mounted off-center and the black-powder filling weighs two pounds.
The Fuze Mk 247 consists of an inertia weight held by a jump-out pin and a creep spring. The detonator is a blank caliber .38 cartridge. When the signal is placed in the bomb, the firing pin assembly is unscrewed and a blank caliber .38 cartridge inserted in the cartridge chamber. The firing assembly is then re-inserted and secured by means of a lock nut. At the time of loading the bomb into the plane, the arming wire is inserted through the jump-out pin, and the safety pin is then removed. Upon release from the plane, the arming wire is withdrawn, allowing the jump-out pin to be thrown free, arming the signal. Upon impact, weighted firing pin overcomes the creep spring and impinges upon the primer of the caliber .38 blank cartridge, which, in turn, ignites the main black-powder charge.