Historic context :
During the Paris Siege in 1871, the German armies could not prevent the escape of numerous airship balloons from the besieged capital to the free south part of France. The improvised use of field guns against these mobile targets moving in altitude proved useless, and the remarkably quick gift by Krupp of 3.7cm guns mounted on pivots on trailer did not give better results mainly because of the lack of an adequate aiming device. This failure had remained in the memories and at the start of the XXth century the increasing development of the airships and airplanes weapons led the German headquarters and industry to invest resources in the design of an artillery dedicated specifically to the anti-airplanes or anti-airships, muich sooner and with more conviction than in other nations.
An incredibly abundant succession of prototypes was invented from 1906 in RheinMetall and Krupp, the calibres evoluting from 5cm to 6.5cm and 7.5cm for an increased power, the barrels being progressively longer for a higher initial speed reducing the time of flight to the target, and the different concepts of automobile, towed of static weapon being experienced. In 1910, the APK (Artillerie Prufungs Komittee) wrote a specification for a anti-airship gun ('Bak' = Ballon-abwehr kanone) that was addressed to the industry, for a AA weapon having a calibre of 7.7cm (already used in the field artillery); towed or automobile, and equipped with a specialized aiming system.
From this specification and based on their experience with the numerous previous prototypes, Rheinmetall and Krupp both proposed in 1913 similar 7.7 cm 27 calibres guns on a pivot ('Sockel Bak') : the '7.7 cm Bak M14 RheinMetall' and the '7.7 cm Bak M14 Krupp'. Both were adopted but only manufactured in a total of 8 automobile or static weapons before the war outbreak, then at a very slow pace until 1916. Indeed, during the first years of the war, Germany preferred the adaptation of 9cm old fieldguns or the transformation of Russina, Italian, Belgian or French captured guns for the production of AA weapons, probably mainly to spare the resources of its artillery industry. Moreover, some of these creations (and particularly the 35 calibres long barrel of the French '75') had better performances than the 7.7cm Bak 1914 !
It is only in 1916, when the allied won the air control, that both industrials were pressed to go back to the design board and quickly propose Flak guns (Flüg abwehr kanone). This gave birth to a modernisation of the 7.7cm Bak L/27 of 1914 with tubes lengthened to 35 calibres for higher initial speeds. Both guns were keeping the main characteristics of their 1914 predecessors, although improved :
These pivot guns, horse towed on a removable trailer platform, were only produced to a quantity of respectively 32 and 36 items, and their mobility proved unsatisfactory on the damaged roads and battlefields grounds. They let the place in 1917 to the newly designed and better performing weapons of 8cm and 8.8cm caliber from both companies engineerings.
- for the '7.7cm L/35 Sockel Flak RheinMetall', a full automatic breech (closing itself at the introduction of a new shell), a tube weight higher at the breech side for a better balance, and a hydro-spring recoil system splitted in two parts around the barrel for a good balance, the spring recuperator being on top of the tube, and the hydraulic brake below it,
- for the 7.7cm L/35 Sockel Flak Krupp, a semi-automatic breech, and an integrated hydro-spring recoil brake / recuperator system located at the top of the barrel.
Technical data :
- Complete description : 7.7cm L/35 Flak 16 anti-aircraft gun RheinMetall on pivot
- Design year : 1916
- Calibre : 77.00 mm
- Weight in firing position : 2058 kg
- Weight for transportation :
- Tube length in calibres : 35.00
- Grooves : 0 unknown
- Projectile weight : 6.85 kg
- Initial speed :
- Fire rate : 15 rounds per minute
- Range : 4750 m altitude max
- Elevation range : -0 to +80 degrees
- Direction range : 360 degrees range