subcalibre

US subcaliber

/ (sʌbˈkælɪbə) /

adjective

(of a projectile) having a calibre less than that of the firearm from which it is discharged and therefore either fitted with a disc or fired through a tube inserted into the barrel
of, relating to, or firing subcalibre projectiles
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012