In this article we examine an explosives safety issue associated with older blasting caps known as the copper azide effect. Early designs (1918-1955) of blasting caps included copper shells filled with lead azide. When moisture comes into contact lead azide, a reaction occurs and hydrazoic acid is formed. Hydrazoic acid is gas at room temperature that is highly toxic and explosive. When in contact with copper, highly sensitive copper azides are formed. Copper azide is more impact sensitive, less friction sensitive, and orders of magnitude more static sensitive than lead azide. Further hydrolysis and oxidation creates what is known as explosive salts.

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Article submitted by UXO Guest Author Rick Stauber. For more information on the UXO Guest Author program, click here.

While the identification features differ greatly between the individual items in the ordnance families, there are identification features that are common that are used in design and manufacturing of those same items.

An example can be found with ordnance that are designed to attack and defeat an armored target utilizing what is known as a "High Explosive Anti-Tank" or HEAT design.

The key technology used in the design of HEAT munitions is the use of a "Shape Charge". A Shape Charge is a cone constructed of soft metal, typically copper. High explosive are packed around the outside of the cone (opposite of how an ice cream cone works). When the explosives are initiated from the rear or base, it implodes or collapses and inverts the cone forming an extremely high velocity pressure wave along the axis of the shape charge. This pressure wave achieves a velocity in excess of 42,000ft/sec and upon impact with the target plasticizes the armor plate at the point of impact. Molten metal as the result of the extreme heat that formed along with the molten metal from the shape charge is projected into the interior of the target, igniting flammable material within the target. Additional damage is created by super-heated gases and high speed pressure wave that accompanies the penetration. Shape Charges are very effective at defeating armor targets including tanks.

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Once an item of military ordnance has been discovered, all attempts should be made to correctly identify it and the condition in which it was found. In many cases older ammunition that is being discovered at various locations are being incorrectly identified and then destroyed. Often, only a single photograph is taken prior to the disposal. In many cases the photograph is out of focus and without accurate measurements being taken.

The purpose of this article is to review proper procedures on how to photograph military ordnance for the purpose of identification. The information is presented for information purposes only. First a safety note: DO NOT MOVE OR DISTURB UNEXPLODED ORDNANCE OF ANY TYPE! RECORD ONLY THAT INFORMATION THAT CAN BE SAFETY OBTAINED WITHOUT MOVING OR JARRING THE ORDNANCE.

Article submitted by UXO Guest Author Rick Stauber. For more information on the UXO Guest Author program, click here.

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When subjected to heat, Ammonium Picrate decomposes and burns like tar or resin. It is relatively difficult to detonate (requires a booster) therefore; it is used in munitions that have to withstand severe shock and stresses before detonating such as armor-piercing bombs and projectiles as well as coastal artillery munitions. Ammonium Picrate us used a main charge for all Navy projectiles over 3-inch caliber.

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The M1 anti-personnel mine clearing device is made up of a flexible linear charge 170 feet long and 1 inch in diameter wrapped in an aluminum cylinder (i.e., large can). The line contains 46 pounds of oil-soaked PETN high explosive. The charge has 19 strands of special detonating cord, which contains 100 grains of PETN per foot. The system is deployed in the field by looping one end of the cable around a stake anchored into the ground as shown in the image below. The looped end contains a booster charge and a threaded cap well, which accepts a 15-second delay detonator for exploding the cable. The oil-soaked PETN cable is projected across the minefield by a JATO rocket motor. Once the cable is shot over the minefield it is detonated. The detonation is meant to disturb anti-personnel mines in its path thus causing them to function thereby clearing a safe path through the minefield.

Source: TM 9-1900 Ammunition General June 1956

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