We had a SMLE barrel adapted with brass rings front and rear for a 3 pounder (or was it a 4" deck gun) Naval gun. Hand extraction and ejection of course. I always wondered about the practicalities of such a beast but............. I mean...., what do they shoot at? Does someone mount a ship target screen at the front of the deck casing? Or do they have a deck gun munted on the 100 yard range at the deck gunners training school? Or just move the ship/submaring into the 25 yard min range as we used to do with the anti-tank guns and tanks when using sub-cal adaptors?