An image detection method based on the ring light section method was developed to measure deep holes with complex surfaces, especially rifled gun barrels.

针对膛线炮身管提出了一种基于环形光切的图像检测方法。

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By the mid 19th-century, rifled barrels were common.

FORBES: No. 7 The Rifle

But it wasn't until 1747, when an English physicist named Benjamin Robins proved that "rifled" barrels performed better, that the practice really took off.

FORBES: Magazine Article