Well by "sinkers" I am referring to discharged guns heading straight to the bottom after you release them having just speared your fish. Previously metal speargun body components were either fully machined from bar or rod stock or dedicated die-castings with thick sections, so there was no inexpensive way to lighten them while maintaining structural strength with a minimum of cutting operations being applied to that component.
The more machining operations used then the more metal can be removed, but problems can occur when the component is turned around to machine it from the other end. When working to close tolerances on thin sections any out of alignment and consequent loss of concentricity will cause break through on thin sections as the cutting tool operates on a slightly different rotation axis to what was used previously in generating the initial cuts. It is attention to such details that makes the Russian "Taimen" an expensive gun to produce on what must be fully automated lathes that control every movement of the component as it is reset for different operations on it.
Hence it will be interesting to see the pattern of cuts made inside that LG rear housing (from both ends) in order to hollow it out enough for it to make the "Revolution" gun a floater without its spear. It should be noted that a metal cutting tool can only remove metal directly in line with the cutting teeth and their axis of rotation, however an undercut can be made such as with a boring bar (or wheel type milling cutter) reaching in and cutting out a recess behind a smaller diameter entrance with a larger annular recess created behind it. This method was used on the "Taimen" rear bulkhead to create a gap behind the air bypass holes (see diagram).
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