CPC Subgroup
B21K 21/14 closed or substantially-closed ends, e.g. cartridge bottoms
Full Title
Making hollow articles not covered by a single preceding sub-group (essentially from sheet-metal or uniform thin-walled tubes B21D, e.g. B21D41/00, B21D51/00) > Shaping end portions of hollow articles > closed or substantially-closed ends, e.g. cartridge bottoms