The earliest muzzle-loading rifles were more difficult to load than smoothbore muskets, but the invention of metallic cartridges made possible the development of breech-loading mechanisms.
The ACR "rifles" used smoothbore barrels to fire single or multiple flechette per round, rather than bullets, to provide long range, flat trajectory, and armor piercing abilities.
The group said in a statement that its fighters carried machine guns, grenades and assault rifles during the hour-long gunbattle, but that none of the militants were hurt.