.45-caliber .45-caliber /ˌdɒt ˈfɔːrtiˈfaɪv-ˈkælɪbər/

adjective

1. [American] Of or relating to the bore of a gun (or its ammunition) that measures forty-five hundredths of an inch in diameter  ( .45 caliber [American] , .45 calibre [Canadian, British] , .45-caliber [American] , .45-calibre [Canadian, British] )
   of or relating to the bore of a gun (or its ammunition) that measures forty-five hundredths of an inch in diameter