The 22.5 cm Minenwerfer M 15 was a heavy mortar used by Austria-Hungary in World War I.

It was a muzzle-loading, smooth-bore mortar that had no recoil system whatsoever.

It was not particularly accurate and bombs often fell over in flight and landed on their sides so they used time instead of contact fuzes.

The M 17 version of this weapon had an elevation screw with a double thread and reinforced trunnion bearings.

Media related to 22.5 cm minenwerfer M15 M16 M17 at Wikimedia Commons