When a flame from an ignited flammable gas enters the conduit and ignites the explosive pack, the bullet is propelled into and frictionally engaging the inlet end of the conduit body such that an internal passageway in the inlet end is substantially blocked to prevent {HEAD ~ the further propagation} of flame upstream into {TAIL ~ the conduit} 
When a flame from an ignited flammable gas enters the conduit and ignites the explosive pack , the bullet is propelled into and frictionally engaging the inlet end of the conduit body such that an internal passageway in the inlet end is substantially blocked to prevent { HEAD ~ the further propagation } of flame upstream into { TAIL ~ the conduit }
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