A shell is a payload-carrying projectile which, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot (AP, APCR, APCNR, APDS, APFSDS and proof shot). Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used. Originally called "bombshell", but "shell" has come to be unambiguous in a military context. "Bombshell" is still used figuratively to refer to a shockingly unexpected happening or revelation.