multicalibre
/ˌmʌltɪˈkalɪbə/Firearms
adjective
Of a gun, piece of artillery, etc.: capable of firing ammunition of several calibres. Also, of ammunition: of several calibres; (in less specific usage) of more than one calibre.
noun
A multicalibre firearm.
Origin
1980s; earliest use found in Summary of World Broadcasts Part 3: Far East. From multi- + calibre.