smoothbore

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.

最早的前装步装弹比滑困难，但金属弹药筒的明促进了后装弹装置的展。

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，以此减时的震动。