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There is a high probability these will not perform adequately on at least a quarter of users simply because they rely on a fit-all multi-flange plug as the passive seal. Very oval, tortuous (twisty)...

Forget the "bone conduction" red herring. It's irrelevant to small arms, all the damaging sound enters via air conduction.

Afraid I can't help you much on commercial options other than to say Starkey through an audiological practice might be a go-er. I have three pairs of custom electronic plugs (re)made from high end...

"Yes" to all your questions but it depends on exactly what you get. Custom plugs, electronic or passive, are only as good as the ear impressions taken and that will vary hugely. Nothing worth having...