Shape of the Bird-Gun Breech

original: "Houmen," literally "Back Gate." This refers to the breech, the rear part of the firearm barrel where the explosion is contained.

Shape of the Muzzle

original: "Qiankou," literally "Front Mouth."

Shape of the Touchhole

Touchhole (Huomen): The small hole at the rear of the barrel where the priming powder is ignited to fire the main charge.

Illustrated Diagram of the Component Parts of the Bird-Gun

Shape of the Screw Thread

Turn left to enter
Turn right to exit
The "Silk Turn" (Sizhuan) refers to the threaded breech plug. The introduction of screw threads was a significant technological advancement in Ming Dynasty firearms, allowing the breech to be sealed tightly yet removed for cleaning.

This type [of ramrod] is inserted into the stock. This is the complete assembly of an old-style stocked bird-gun.

The ramrod is that which is inserted into the interior [of the stock or barrel slot]. It is now illustrated separately here for clarity.
The ramrod (Shuozhang) was essential for seating the lead ball and wadding against the gunpowder charge.