Other compounds act as sensitizers and binders.Įxplosives used include azides, fulminates, diazo compounds, nitro or nitroso compounds, for example, lead or silver azide, mercury fulminate, lead styphnate, TNT, and PETN (which also act as sensitizers). Generally speaking small arms primers consist of an explosive, an oxidizer, a fuel, and a frictionator. Flame bursts from various primers were found to have effective durations varying from 400 to 750 microseconds and total durations varying from 650 to 1,500 microseconds.45 The incandescent particles are thought to promote ignition by thermal radiation. The percentage of the weight carried as incandescent particles by the hot gases will vary with the composition, but can be in the region of 70%. For a typical priming composition of 0.15 g, the volume of gases at room temperature and pressure is in the order of 1.5 cm. The rate of burning, volume of gases, weight of solid particles produced, and the duration of the flame are the major influences on the efficient functioning of a priming composition. The presence of a binding agent prevents such separation as well as fixing the composition in the desired position in the assembly. Nonuniformity of composition due to physical separation caused by shaking can lead to great variations in sensitivity and even failure to function. Sometimes this is more important than the proportions of the ingredients. The sensitivity of priming compositions varies, but that of an individual composition can also be varied to some extent by careful control of the granulation of each of the ingredients. The additions may also serve to increase the volume of gases produced per unit weight of priming composition, to prevent the gases from having too high a temperature, and to contribute incandescent solid particles to the decomposition products. Fuels are necessary to prolong the combustion long enough to ignite the propellant. The oxidizing agents provide oxygen to support combustion of the fuel within the small space of the cartridge case. In some cases a single addition may serve two purposes, for example, antimony sulfide acts as a fuel as well as a sensitizer to friction, and gum arabic acts as a fuel and a binding agent. The net effect of the additions is to dilute the initial detonating agent so as to convert its decomposition from detonation into rapid combustion. In fact, most priming compositions consist of mixtures of one or more initial detonating agents, with oxidizing agents, fuels, sensitizers, and binding agents. The next most desirable type of priming composition would be a mixture of compounds that, although individually nonexplosive, sensitize each other to ignition and rapid burning. In practice, no single chemical compound meets all the requirements of an ideal primer. The only compound to even approach these specifications is lead dinitroresorcinate however, it is far too sensitive. The ideal priming composition would consist of a cheap, readily available, relatively safe to handle, simple chemical compound of uniform granulation which when subjected to impact would undergo rapid, highly exothermic decomposition. A priming composition must deliver a relatively large volume of hot gases and hot solid particles without the development of a detonating wave. Priming compositions for firearms ammunition are mixtures which, when subjected to percussion, provide a sudden burst of flame that serves to ignite the propellant within the cartridge case.

Antimony sulfide