above u201d and u201c below u201d and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention however when applied to equipment and methods for use in wells that are deviated or horizontal such terms may refer to a left to right right to left or other relationship as appropriate moreover in the specification and appended claims the terms u201c pipe u201d u201c tube u201d u201c tubular u201d u201c casing u201d u201c liner u201d and or u201c other tubular goods u201d are to be interpreted and defined generically to mean any and all of such elements without limitation of industry usage fig1 represents the essential invention environment showing a partial perforating gun assembly including a firing head 10 a drop sub 12 and a perforating gun tube 14 these are independently severable units that may be unitized by integrally threaded box and pin joints such an assembly may be suspended into a well bore by wireline coiled tubing or pipe joints in traditional practice the perforating gun 14 is a tube having a multiplicity of explosive perforating charges 16 set within the tube shell to discharge radially against a production pipe well casing or raw bore wall the objective of such perforations is to facilitate the flow of in situ fluids gas or crude petroleum from a fluid bearing earth stratum into an inner flow chamber these explosive charges 16 are often set in a helical pattern around and along the length of the.