1. 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.
   最早的前装步枪装弹比滑膛枪困难，但金属弹药筒的发明促进了后膛装弹装置的发展。
2. 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.
   炮弹（抛射物）必须拥有稳定的外形，比如带尾翼的箭状物或球体，以此减小发射时的震动。

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