膛线

Traditional form:

膛線

Pinyin (reading):

tángxiàn

Definitions:

• rifling (helical grooves inside the barrel of a gun)

Characters:

• 膛 - chest cavity; hollow space
• 线 - line, thread, wire; clue, trail

Traditional characters:

• 膛 - chest cavity; hollow space
• 線 - line, thread, wire; clue, trail