any of the bivalent metals of group II of the periodic table (calcium or strontium or barium or magnesium or beryllium)

a metal block in breech-loading firearms that is withdrawn to insert a cartridge and replaced to close the breech before firing

a metal block in breech-loading firearms that is withdrawn to insert a cartridge and replaced to close the breech before firing

a metal block in breech-loading firearms that is withdrawn to insert a cartridge and replaced to close the breech before firing