placed across and secured to one end of the tube the tube is then filled with powder 80 and metal plug 72 placed in the end opposite plastic sheet 74 one end of wire 78 is trapped between the plug and tube and the excess trimmed off the metal spacer 76 which has an opening 82 in its base is now secured to the end of the tube opposite metal plug 72 the other end of wire 78 is trapped between the tube and spacer 76 in assembling ignitor assembly 22 an insulative washer 84 is placed in the large first section 34 of passage 32 so that it abuts against shoulder 38 primer unit 28 is placed in the large section 34 and end 86 of outer body 24 is peened over to the position shown in fig2 this locks primer unit 28 in place other means for locking it in may also be used the assembled contact unit 26 is now placed into the small second section 36 of passage 32 so that tip 64 of center post 46 presses metal plug 72 in the primer unit through washer 84 unit 26 is held in place by the outwardly extending fingers on retention spring 42 the ignitor assembly 22 is threaded into piston 18 and that unit is.