Drawings: Automatic-gun Wagon / Artillery Wagon
The origin of these wagons is a mystery for a large part. Two of these wagons were captured during Finnish Civil War in 1918. But since existing photos are from later date, it is not known for sure if they were originally build in Fredriksberg Engineering Works with their unusual gun-turrets and automatic-gun armament, or if this was a modification made later that same year. What is certain is that the way how the armour plating has been riveted is similar as done in other armoured trains manufactured for the Finnish Red Guards in Fredriksberg Works during Finnish Civil War in 1918. However none of the other Fredriksberg-made armoured trains had rotating gun turrets or 37-mm automatic cannons as main weaponry, which makes these two wagons very different. Even if Fredriksberg Works was the manufacturer of these two automatic-gun wagons, it is quite likely that the turrets were manufactured somewhere else. One possibility could be that the turrets originated from some outdated Russian warship and the Bolsheviks of Baltic Navy delivered them to Finnish Reds, who used them as building materials of armoured train. But this still remains no better than just one possibility. The time line before first existing photograph leaves also room for Finnish or German made modifications around 1918 - 1919. Since the Finns captured some 37-mm Maxim automatic guns in 1918 and also the Germans both manufactured and used this early automatic cannon, both of these options seem also possible.
As mentioned 37-mm Maxim automatic gun was the main weapon of this wagon. This weapon had been installed to rotating turret, whose firing sector seems to have been less than 270 degrees. While some countries (like Germany) had used 37-mm Maxim as anti-aircraft gun this weapon had poor ballistics for this use and in this particular case the turret didn't allow enough elevation even for trying this kind of use. Already year 1918 the original 7.62 mm x 54R calibre Maxim machineguns were replaced with German 7.92 mm x 57 JS calibre MG-08 medium machineguns and MG-08/15 and MG-08/18 light machineguns. Early 1930's these German machineguns were again replaced with 7.62 mm Maxim as Finnish military was getting rid of 7.92 mm x 57 JS calibre weapons.
As with artillery wagons after Winter War also these wagons were re-armed with 40-mm Bofors anti-aircraft guns (40 ItK/39 B to be exact) and the original closed gun turrets were removed. During Continuation War these wagons went through series of changes and the last remaining wagon, which is in Finnish Armour Museum nowadays, looks quite different when compared to photos of early Continuation War.
PICTURE: Automatic-gun wagon in use of Finnish Army in 1920's. CLICK THUMBNAIL TO SEE LARGER PIC (43 KB).
PICTURE: OK-type 4-axle artillery wagon during Winter War in February of 1940. Notice the change of main weaponry, modifications of roof and chimney, which are visible in some period photos. CLICK THUMBNAIL TO SEE LARGER PIC (40 KB).
PICTURE: OK-type 4-axle artillery wagon in February of 1940. This drawing shows the roof opened and three water-cooled 7.62-mm Maxim medium machineguns used anti-aircraft machineguns placed there. CLICK THUMBNAIL TO SEE LARGER PIC (62 KB).
PICTURE: OK-type 4-axle artillery wagon in summer of 1942. Likely this wagon version was used in Armoured Train 1 at the time. The wagon has 40 ItK/39 B anti-aircraft gun, three water-cooled 7.62-mm Maxim medium machineguns for anti-aircraft use and another few water-cooled 7.62-mm Maxim machineguns installed to portholes in sides of the wagon for shooting surface targets. CLICK THUMBNAIL TO SEE LARGER PIC (61 KB).
PICTURE: OK-type 4-axle artillery wagon shown as it was in summer of 1942. This wagon version was used in Armoured Train 2 at the time. Besides the usual Maxim machineguns the wagon has one 76 ItK/02/34 OH and one 40 ItK/39 B anti-aircraft gun. CLICK THUMBNAIL TO SEE LARGER PIC (66 KB).
PICTURE: OK-type 4-axle artillery wagon shown as it was in summer of 1943. This wagon version was used by Armoured Train 1 at the time. The wagon has received its second 40 ItK/39 B anti-aircraft gun. CLICK THUMBNAIL TO SEE LARGER PIC (61 KB).
PICTURE: OK-type 4-axle artillery wagon belonging to 1st Railway Anti-Aircraft Artillery Battery in summer of 1944. This drawing is based to final version of this wagon and visible are the modifications presumably made as part of the repairs in summer of 1944. Main weaponry of this wagon are two 40 ItK/39 B anti-aircraft guns. CLICK THUMBNAIL TO SEE LARGER PIC (61 KB).