10 cm tower howitzer THM9 - 10-cm-Turmhaubitze T.H. M.9
The 10 cm tower howitzer TH M9 , consisting of an armored dome and cannon, was part of the more modern Austro-Hungarian fortifications during the First World War . The Škoda works in Pilsen were the manufacturer of all armored domes .
For the main armament of the new fortifications on the border with Italy and in Bosnia-Herzegovina , the original draft of the Colonel of Genius Otto Ellison von Nidlef provided for a separation of the gun carriage and turret , contrary to the usual application . This meant that the gun and turret were not rigidly connected to one another. Since the howitzer is a minimal charter cannonwas carried out, the whole tower did not have to be set in motion every time in the small side straightening area. Furthermore, it was feared that when it was fired, vibrations could arise that could possibly be transmitted to the gun via the tower bell and damage it. Another advantage was the possibility of expanding the gun with mount if necessary and using it elsewhere. The domes were made of very tough chrome-nickel steel (so-called P-2 steel) with a tensile strength of 45 kg / mm².  The production costs for the dome and carriage amounted to 90,000 crowns .
First, the prototype of a cannon dome with the designation M6 was made. This had a wall thickness of 160 to 200 mm, the pipe length was 1.475 m (L13). The dome weighed 15.8 t and was 20 cm shallower than the later model M9. However, this limited the negative elevation range to −8 °, which turned out to be unacceptable. In 1908 this dome was blown up on the artillery firing range in Felixdorf with a load of 25 kg of ecrasite . The dome was externally intact except for a 16 mm deep indentation, but inside, as with the impact of a crush-head grenadeMetal blasting caused damage to the mechanics of the gun (this prototype, which had only twelve lateral straightening teeth, was later installed as a medium gun in the Gschwent factory ).
It was then decided to use different dimensions for the series production. The dome was given a crown thickness of 25 cm and a higher vault. The elevation angle could be improved to −15 ° by making an additional change to the pipe feeder. The maximum reference height was + 43 °, which made it possible to place shrapnel directly above the apron of the fortifications with the weakest load . The inner diameter of the armored dome was 2.68 m, the weight was 18.7 t. The dome was on a two-part armor made of 25 cm thick cast steelput on with a weight of 16.5 t. The armor was embedded in the concrete ceiling of the plant to a depth of 1 m. Access to the tower was via a staircase from below from a postern. This transition represented a weak point that was protected with an additional tank. Inside the dome was a revolving platform that sat at the bottom of the gun well. If the tower was to be rotated, it was raised by one millimeter by means of two lifting devices using four rubber buffers (the load was now on the platform), swiveled to the specified position and lowered again. The ring bead on the upper edge of the armor had 24 horizontal bores on its underside, each offset by 15 °. In these, the turret was locked in the firing position with the help of a locking bolt, so that the turret dome could not be twisted and wedged in the event of a side shell impact. The Feinrichtung was then carried out via the gun itself, which was moved by the Minimal Schartenlafette by +/- 11, 25 ° could be readjusted. The rotation in the segments took at least 15 seconds. To prevent the dome from being thrown off, six claws reached under the armor and secured it in this position. The tower could be raised up to 10 millimeters to remove jams. Firing with the tower dome raised was possible.
In the peacetime, a sheet metal cover was used as weather protection, which was placed over the entire dome. When preparing for combat readiness , only the openings in the dome were covered by a sheet metal hood. This was hung on a transverse bar above the openings.
The gun was a further development of the M99 field howitzer . The caliber was 104 mm, the barrel length 176.5 cm (L / 17). The pipe itself was made of cast bronze with a progressive twist, a right-hand flat wedge lock with sleeve cover and a hydraulic return brake. It was mounted in a forward pivot mount that was attached to the pivoting platform. The carriage had two lifting devices, a toothed arch leveling machine with worm gear and a relief device. The lateral direction took place via a worm drive. With a muzzle velocity of 370 m / s, both theShrapnel grenade M9 as well as with the high explosive grenade M11 a maximum range of 7.3 km can be achieved. The target was set using a telescopic sight, which was very modern for the time, with an independent attachment. The rate of fire was a maximum of ten rounds per minute. It was installed in a depression mount.
The most commonly used ammunition was the M9 shrapnel grenade with a weight of 16.2 kg and a filling of 758 11.7 mm lead bullets. In addition, the M11 ekrasite grenade was used. All ammunition of the light field howitzer M99 could also be fired. The fired shell casings were refilled in the manipulation room of the fortress itself and loaded with 1st to 8th charges. In order to ward off infantry attacks, it was possible to keep the fuses of the shrapnel grenades at a temperature of up to 5 m.
Although the armored domes themselves could not be penetrated by the Italian 30.5 cm coastal mortars,   the armor and coverings proved to be too weak. The gun wells were literally shot free several times, whereupon the entire gun turrets overturned. The armored armor was also penetrated several times, which in individual cases led to the armored domes being thrown out. The range of the howitzers was not sufficient for all plants to catch fire from the Italian armored plants Forte Monte Verena and Forte Campolongo, which were equipped with 15 cm long-barreled gunsto reply. To make matters worse, they were up to 500 m higher. The howitzers and their mounts were therefore moved to field positions where they served well.
The weak points in the armor were recognized in 1913 when attempting to fire with the M11 mortar (30.5 cm), albeit too late. A successor model (TH M14) was then designed for the 10 cm and 15 cm tower howitzers with a 2.30 m deep and 30 cm thick armored armor. The armor of the dome was reinforced to 30 cm. This increased the weight of the dome to 22.5 t and that of the armored car to 51 t. Intended for installation in the Valmorbia plant , work on it was canceled due to the outbreak of war.
- The toughness was given priority over higher hardness.
- the Italian mortars 30.5 cm were not able to fire with the optimum barrel elevation. As a result, the maximum impact force was not achieved
- In the Gschwent plant, a 30.5 cm shell hit a tower dome as a dud at a shallow angle about 20 cm above the support joint. The bullet penetrated 19 cm deep into the armored steel and got stuck without causing damage inside.
- Rolf Hentzschel: fortress war in the high mountains. Athesia, Bozen 2008, ISBN 978-88-8266-516-6 .
- Erwin Anton Grestenberger: Imperial and Royal fortifications in Tyrol and Carinthia 1860–1918. Verlag Österreich ua, Vienna 2000, ISBN 978-3-7046-1558-9 .