The 20 cm Luftminenwerfer M 16 (Pneumatic trench mortar) was a heavy mortar used by Austria-Hungary in World War I. It was developed by Austria Metal Works in Brno from their earlier 12 cm Luftminenwerfer M 16. It was a rigid-recoil, smoothbore, breech-loading design that had to be levered around to aim at new targets. It was very simple in that the shell closed the top of the chamber and was retained by a "gripper" until the air pressure was deemed sufficient and the gripper was manually released, which fired the weapon. The barrel was fixed at 45° elevation and range was adjusted by varying the air pressure, but an additional barrel could be fitted to extend the range. A single cylinder of compressed air was only good for four to six shots. It was loaded onto a two-wheel cart for transpo