 Subsonic cartridges fire bullets slower than the speed of sound so there is no sonic boom.This means that a subsonic cartridge, such as .45 ACP, can be substantially quieter than a supersonic cartridge such as the .223 Remington, even without the use of a suppressor.Bullets do not normally contain explosives, but damage the intended target by transferring kinetic energy upon impact and penetration (see terminal ballistics).