Composition of primer is

The primers are composed of lead styphnate, barium nitrate and antimony sulphide. Most centrefire primers are composed of all the three compounds. The detection of these compounds constitutes the basis for the tests to determine whether an individual has fired a firearm. In case of rimfire ammunition, the primer composition is spun into the rim of the caridge case with the propellant in intimate contact with this composition. On firing, the firing pin strikes the rim of the caridge case, compressing the primer composition and initiating its detonation Ref : Krishnan vij Textbook of Forensic medicine and Toxicology 5th edtion ; pg no - 237