Historic context :

The experience of the positions war and the multilipcation of the parallel lines of the trench network made the fighting units ask for a range increase of the 250 mm trench mortar, whose power and relative mobility had transformed into a feared weapon in this kind of conflict.

From 1916, RheinMetall delivered a new model named '25 cm sWM n/A' ('sMW' = 'schwerer MinenWerfer' = heavy mine launcher; 'n/A' = 'neue Art' = New version). The considerable increase of the barrel length, growing from 3 to 5 calibres (762 mm to 1090 mm), and a reinforcement of the recoil recuperation system allowed to increase the range (now close to 1 km) with limited weight increase of the gun, gaining +120 kg and whose setting into battery required up to 28 men according to the manual !

A part of the old a/A materials were modernised by screwing onto the old short tubes an extension. These weapons were sometimes named '25cm sMW n/A 16a'.

The manufacturing of the heavy mine launcher never stopped during the war. Compared to the 44 mortars available at the war outbreak, 1196 'a/A' and 'n/A' 25cm mortars were in service in June 1917.

Technical data :

• Complete description : 25cm heavy trench mortar new mark
• Design year : 1916
• Calibre : 250.00 mm
• Weight in firing position : 780 kg
• Weight for transportation : 1077 kg (with the 232 kg platform and the wheels)
• Tube length in calibres : 5.00
• Grooves : 6 34.44 mm wide; 7 degrees angle
• Projectile weight : 97 kg (mine raccourcie 70 kg)
• Initial speed : 51 m/s (105 m/s for the short mine)
• Fire rate :
• Range : 563 m (750 m for the short mine)
• Elevation range : 45 to 75 degrees
• Direction range : 20 degrees total range

• German Artillery of World War One           Herbert Jager                   Crowood   2001  
• Die deutschen Minen- und Granatwerfer im Ersten Weltkrieg 1914-1918       Dr Tillmann Reibert                   epubli GmbH   2014  
• Das Ehrenbuch der Deutschen Pioniere       Major Paul Heinrici                   Verlag Tradition, Berlin   1931  
• German Trench Mortars and Infantry Mortars 1914-1945       Wolfgang Fleischer                   Schiffer Military / Aviation History   1996