Practice Bombs of WWII

© Jerry Penry


The MK-19 practice bomb was used for high-altitude horizontal bombing. The MK-19 had an overall length of 13.06". The diameter at its largest point was 2.62". The fins were 3.67" in length. The main body was made of lead-antimony while the fins were made of steel. The weight, when armed, was approximately 13 lbs-2 oz. The spotting charge was a 10-gauge shotgun shell as the signal (AN MK-4) as explained below. This bomb could be used against armored-deck target boats have a 1/2" armor deck. The maximum altitude at release could not exceed 6,000 feet which was far greater than the altitude of 2,500 feet for both the smaller MK-5 and MK-43 practice bombs. Five bombs could be carried in the MK-43 Bomb Rack and eight could be carried in the MK-47 Bomb Rack. (If the above information is in any way incorrect, please contact me)

The AN MK-4 spotting charge consisted of an extra long 10-gauge blank shotgun shell that was inserted into the hollow chamber of the bomb. The primer end of the shotgun shell was downward so the blast would go upwards through the tail section upon impact. In the nose of the MK-19 were two small holes where a cotter pin was inserted. This pin went into a firing pin which then fired the primer on the shotgun shell. There were two slightly different firing pin assemblies that were interchangeable and functioned basically the same. The shotgun shell fit loosely in the chamber when inserted into the nose, but it could not fall out the bottom. There was a space between the primer end of the shotgun shell and the firing pin. Upon impact, the inertia caused the shotgun shell to come forward into the stationary firing pin. The other firing pin design had the inertia of the hit drive the firing pin backwards into the shotgun shell.

AN MK-4 Bomb Signal

The above drawing shows the extra long 10-gauge shotgun shell used for the signal.

From the Ordnance Pamphlet 1280 "Aircraft Bombs" 17 February 1945.
The Miniature Practice Bomb Signal AN-MK 4 is a "blank" No. 10 gauge shotgun shell (extra length). The signal has a metal base and base flange fitted to a cardboard shell. The components of the signal are: a No. 7 U.M.C. primer with an expelling charge of black powder separated from a charge of pyrotechnic (red phosphorous pyrotechnic mixture No. 7) by a kraft paper disc glued to a No. 10 gauge gun wad. The charges are sealed by a No. 10 gauge paraffined-edge felt gun wad and secured by crimping over the paper shell casing. The weight of the loaded signal is 2.1 ounces.
Note: Under no condition are these signals to be opened or tampered with. Defective signals will be returned to an ammunition depot or turned over to a Bomb Disposal Officer for proper disposal.
Signals are packed 25 to a cardboard carton. The outside dimensions of the carton are approximately 4.4 inches long, 4.4 inches wide, and 6.125 inches deep. Twenty filled cartons are packed in a wooden packing box of the type used for packing commercial No. 10 gauge shotgun shells. The outside dimensions of the packing box are approximately 25.5 inches long, 14.25 inches wide, and 10.75 inches deep. Miniature Practice Bomb Signals AN MK 4 will be stowed in approved storage facilities. The temperature of the storage facility shall not exceed 100F., and the signals shall be protected from direct sunlight, spray, or moisture and shall not be subject to excessive motion or vibration.


Extra long 10-gauge shotgun shells used for the MK-19 practice bomb.

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