Controlled Buoyancy Perforating technology for highly deviated and substantially horizontal wellbores may include long perforating guns assembled on a rig floor from a multiplicity of light weight and highly engineered shaped charge carrier joints. Tubular housings for such light weight joints may be fabricated from composite materials having steel transition collars. The collars are designed for an angularly coordinated, bayonet assembly and, in most cases, rapid disassembly. The internal volume of each joint is environmentally sealed by a plurality of O-rings. Barbs carried by collet fingers projecting from opposite ends of a sealing sleeve that externally bridges a transition collar union plane secures the union by meshing with detent channels in the respective collars. Individual shaped charge units and cooperative fusing are assembled in a light weight inner loading tube having an alignment collar to secure the angular and axial position of the loading tube relative to the transition collars.