made of metal this adaptor confines for a minimum of the first 1 4 inches of its length the igniter strand in order to obtain the desired propagation velocity of 1300 1500 meters per second without the use of this adapter to confine the end portion of the igniter strand 22 the igniter strand propagation velocity would be only 300 meters per second the cylindrical adapter 26 also acts to maintain in position the end 24 of the igniter strand 22 to accept the energetic output of the primer head assembly 12 the primer head assembly 12 may be any conventional head loading assembly provided its output is equivalent to approximately 3 grains of black powder the ignitor charge 16 may be black powder or may be also boron potassium nitrate which performs equally well our tests of the combustible primer in accordance with this embodiment of the invention the results of which are shown in the table below were conducted using mil p 223 b black powder class 1 in a m865 tank cartridge these results illustrate that the primer of the present invention functions comparably to the standard m865 practice cartridge having a standard m125 metal tube primer __________________________________________________________________________m865combustible primer.