The German victory on Russian armies in Tannenberg in 1914 gave a very impressive loot, including numerous good Russian fieldguns 76.2mm Putilov M1902 and huge stocks of ammunitions. The idea came very quickly to convert these excellent weapons into anti-aircraft guns.

The very first such adaptation was made by Rheinmetall, using the Russian gun tube and hydro-mechanical recuperator on a specifically designed fork mounted on a rotating conical pivot. This adaptation needed to move the trunnions backwards in order to limit the recoil length and allow vertical firing. Therefore the desequilibrated tube had to be supported by a compensating piston.

This generic Rheinmetall design was used on different supports, such as the :

• 7.62 cm Ortsfeste Flak generic and most common fabrication fixed on a concrete base
• 7.62 cm WagenFlak on a horse-driven platform
• 7.62 cm EisenbahnFlak on railcar

Main characteristics :

• Weight in firing position : unknown
• Calibre : 76.2 mm
• Tube length : 30 calibres
• Projectile weight : 6.58 / 7.45 kg
• Initial velocity : 593 / 588 m/s
• Maximum range : 5600 m altitude
• Elevation range : unknown
• Direction range : 360 degrees