Historic context :

Clearly inspired by the French 58 Nr 2 trench mortars, of which they had built a Russian '58 FR' version in 1915, the Izhora Works (Petrograd) designed in 1916 a heavy version based on the same characteristics as these kinds of weapons.

Indeed, the '89 mm Izhora heavy mine launcher' was still having a smooth bore barrel in which the servants could insert the solid tail cylinder of a fin tailed bomb, but with a scale factor allowing it to increase considerably the weight of the ammunitions. This way this heavy version was able to fire a frightening fin tailed bomb of 290/89 mm weighing 79.9 kg, while the French and Russian versions of the 58 Nr 2 were using already powerful bombs of 16 to 45 kg.

In order to make it possible, all the mortar dimensions had been incresed : the barrel inner diameter was changed from 58 to 89 mm, and its length from 550 à 1194 mm. The total weight in combat position, including its wooden base, was 737 kg instread of the 410 kg of the French 'small model'. Its transport on short distances was made by adding two wheels, but on longer distances a horse driven car (4 horses / 4 wheels) was necessary.

Depending on the sources, the number of produced items until 1917 varies from 43 to 133 mortars, out of an initial 900 weapons order.

Technical data :

• Complete description : 89 mm heavy mine-thrower Izhora
• Design year : 1916
• Calibre : 89.00 mm (tail of the projectile)
• Weight in firing position : 239 kg
• Weight for transportation : 344 kg
• Tube length in calibres : 0.00 1194 mm
• Grooves : 0 smooth bore
• Projectile weight : bombes empennées explosives de 290/89 de 79.9 kg, ou de 320/89
• Initial speed :
• Fire rate :
• Range : 850 m (79.9 kg bomb)
• Elevation range : +30 to +70 degrees
• Direction range : unknown

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