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.

最早步膛困难，但金属药筒发明促进了后膛置发展。

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.

炮（抛射物）必须拥有稳定外形，如带尾翼箭状物或球体，以此减小发射时震动。