One more item for the non-believers and I'll let this dead horse lie/lay, consider fire-arms prior to the breechloader; there wasn't any such projection. The advancement in breech-loader technology led to a stringcourse or protrusion from the standing breech(face) where previously the plugs of the tubeset married with the standing breech. I'm not sure when the term action flats arrived on the scene, and maybe I should look, but all the action was aft of the frame. So it is possible, & I could be totally off base here, that with the arrival of the boxlock/body action, the term action flats was pressed into use. Let me see if I can locate a dissembled Lefaucheux action. It is possible that the term water-table may pre-date action flats.
Kind Regards,
Raimey
rse
