This gun dates to the early 1900s so it was actually fairly old by the 1920s. Contemporary artillery either used screw breech mechanisms with the powder charge loaded in fabric bags and obturation (sealing of the breech against the escape of gas) being accomplished with some form of De Bange rubber pad or some form of sliding wedge with the powder loaded in a metallic cartridge case (with or without the projectile attached) which would expand on firing and provide obturation just like in small arms.

The first form was slower to load but the ammunition was cheaper and lighter while the second allowed for much faster firing. How and what was chosen varied widely within Contemporary militaries. That said it was rare to see a cannon with a screw breech AND using metallic cases for the powder charge.