is cut into the structural wall of the loading rod 30 adjacent the second bi directional booster 44 to provide an ignition initiation window 52 between the second bi directional booster 44 and the adjacent main load explosive pellets 40 a larger coil spring 54 surrounds the lower end of the load rod 30 to apply a resilient bias between the nose plug 14 and the end most main load explosive pellet 40 in the embodiment shown in fig1 a third bi directional booster 46 can be secured within an aperture 13 shown in fig3 that penetrates the transverse wall 32 i e inside face wall of the top carrier plug 12 to position the third bi directional booster 46 in detonation proximity of the initiating explosive 22 as further shown in the embodiment of the present invention shown in fig1 a fourth bi directional booster 48 can be secured to the lower timing spool sleeve 39 the third and fourth bi directional boosters 46 and 48 can be linked by a second mild detonation cord 45 which has substantially the same length as the first mild detonating cord 43 however the intermediate length of the second detonation cord 45 is wound about the flutes 36 on the timing spool 34 surface the distal end of the nose plug 14 can be tapered back from.