Historic context :

In 1914, Austro-Hungaria was having no heavy trench mortar for its Army. Having tested before the war the brilliant German 25cm sMW minenwerfer of Rheinmetall, it ordered 40such weapons and requested their manufacturing under licence by the Austrian company Böhler. This latter however never received the needed assistance from the German company, too busy with its own country war needs.

Consequently, the Army Technical Commission decided in autumn 1914 to request Böhler to manufacture a prototype designed before. After some tests and improvements, the heavy minenwerfer was adopted, and a 40 weapons order issued as soon as November 27, 1914.

The '22.5 cm MW M15', whose profile was easily recognizable with its two huge frontal screws dedicated to the vertical aiming, was delivered to the armies from June 1915. Appreciated for its simple design as well as for the power of its shells, this smoothbore mortar, muzzle loaded and without any recoil recuperation system was although lacking of precision, and subject to duds (when its bomb landed on its side on soft grounds). It could launch both high explosive shells and gaz shells. For transportation, it was equipped with M99 mountain gun wheels.

This mortar had 3 successive versions with increasing barrel lengths. Besides this, whereas the M15 and M16 seemed pretty similar, the M17 could be identified thanks to its double thread screws, and a narrower platform (52 cm vs 66 cm). The Austrian Army was owning as much as 930 such units in the end of 1917.

Technical data :

• Complete description : 22.5cm pneumatic trench mortar M 1915, 1916 et 1917 Bohler
• Design year : 1915
• Calibre : 225.00 mm
• Weight in firing position : 565 kg
• Weight for transportation :
• Tube length in calibres : 3.60 (M15) - 4.2 (M16) - 4.9 (M17)
• Grooves : 0 smooth bore
• Projectile weight : 65 et 76 kg (deux types d'obus explosifs - court et long), et obus à gaz
• Initial speed : 170 m/s
• Fire rate : 2 rounds / minute
• Range : 210 to 800 m (M15)
• Elevation range : +25 to +75 degrees
• Direction range : none