炮管

nà xiē chén zhòng de dà pào shēn xiàn zài ní li zhǐ lù chū pào guǎn

那些沉重的大炮深陷在泥里，只露出炮管。

The heavy guns sank up to their barrels in the mud.

guān yú pào guǎn de zhī shi

关于炮管的知识

the knowledge of rifled barrels