..............Two problems with a recessed ejector pin. One is that it doesn't end ALL lube there at the BB, just most of it. In order to be practical the outter circumfrance of the lip has to have a bit of a flat on top as a true knife edge would be fragile and could eventually be ruined by catching on the lube holes. Second problem is that now THAT ejector pin is ruined for regular FB slugs.
.............Buckshot