21 cm Mörser M1880
The 21 cm Festungs und Belagerungs Mörser M1880 or in English was a heavy mortar designed by Krupp that armed several European countries before and during World War I. Wikipedia
Breech: Horizontal sliding block
Effective firing range: 6.2 km (3.9 mi)
Muzzle velocity: 200 m/s (660 ft/s)