These were Škoda guns built at the Pilsen works. Fitted to Austria-Hungary's last pre-dreadnoughts and to her only completed dreadnoughts. Used a horizontal wedge breech. Unlike German guns of this caliber, there was no "fore charge" used in these weapons, all the propellant charge was in a single brass case.

The Škoda Works of Pilsen produced a total of 65 guns (5 of them were spares) in this caliber. The first 13 were for the Radetzky class and the second 52 were for the Tegetthoff class (also known as the Viribus Unitis class). Only the second series, the guns for the Tegetthoff class, were designated as K10. The K10 differed slightly from the earlier 30.5 cm (12") guns in that its chamber was 1.97 inches (5 cm) longer, which allowed these guns to use a heavier propellant charge.

Radetzky, Erzherog Franz Ferdinand, Zrínyi and Tegetthoff were ceded after World War I to Italy, where they were scrapped and their guns then used as coastal artillery.

Actual bore diameter was 30.50 cm (12.008 inches).

Gun Characteristics

Designation 30.5 cm/45 (12")
30.5 cm/45 (12") K10
Ship Class Used On Austria-Hungary
   30.5 cm/45 (12") - Radetzky class
   30.5 cm/45 (12") K10 - Tegetthoff class

   Coastal Artillery

Date Of Design 1908
Date In Service 1910
Gun Weight 116,070 lbs. (52,650 kg)
119,600 lbs. (54,250 kg) including BM
Gun Length oa 541 in (13.750 m)
Bore Length about 512 in (13.000 m)
Rifling Length 417.6 in (10.606 m)
Grooves (92) 0.115 in deep x 0.271 in (2.92 mm x 6.9 mm)
Lands 0.138 in (3.5 mm)
Twist RH 1 in 25
Chamber Volume N/A
Rate Of Fire 3 rounds in first minute with ready ammunition, 1 to 2 rounds per minute afterwards


Type Separate
Projectile Types and Weights Austria-Hungary 1
   APC L/3,4 2crh - 992 lbs. (450 kg) 2
   APC L/3,7 4.5crh - about 996 lbs. (452 kg) 2
   APC L/4,3 5crh - about 1001 lbs. (454 kg) 2
   SAPC L/4 3 L/4,0 - 992 lbs. (450 kg)
Bursting Charge APC - 8.8 lbs. (4.0 kg) TNT
SAPC - 58.9 lbs. (26.7 kg) TNT
Projectile Length APC 2crh - 40.8 in (103.6 cm)
APC 4.5crh - about 44.7 in (113.6 cm) 4
APC 5crh - about 51.9 in (131.9 cm) 4
SAPC - about 48.4 in (122.9 cm)
Propellant Charge 5 Non-K10 - 302.0 lbs. (137 kg) 25/660 mm M97 f.R.P.
K10 pre-war - 308.6 lbs. (140 kg) 25/660 mm M97 f.R.P. 6
K10 about 1913 - 313 lbs. (142 kg) 7
Cartridge Case Size and Weight 305 mm x 1,372R 8
153.4 lbs. (69.6 kg)
Muzzle Velocity Austria-Hungary
   2,625 fps (800 mps)

   2,510 fps (765 mps) 9

Working Pressure 18.4 tons/in2 (2,900 kg/cm2)
Approximate Barrel Life 200 rounds
Ammunition stowage per gun Radetzky - 75 - 76 rounds 10
Viribus Unitis - 82 rounds 11
  • ^The Italians found many projectiles for these guns in the city of Pola when they occupied it after the war. It seems unlikely that they ever produced their own projectiles.
  • ^ original AP projectiles for these guns were 2crh and had an AP cap but no ballistic cap. About 1912-13 the navy refitted these projectiles with ballistic caps which made them about 4.5crh. This overall length was limited by the hoists on the Radetzky class. The hoists on the later Tegetthoff class could accommodate longer shells, and these ships were accordingly given 5crh ballistic caps. It is probable that the 4.5crh and 5crh shared the same shell body and AP cap with the only difference being the ballistic cap. See sketches below. Weights given here for the APC 4.5crh and APC 5crh projectiles are my estimates based upon notes in "Naval Weapons of World War Two." Actual designation for APC was "bekappte Panzergranate."
  • ^SAPC projectiles were made both with and without an AP cap. See photograph below of an existing SAPC with a cap. Actual designation for SAPC was "Zündergranate."
  • ^4.14.2Lengths of APC 4.5crh and APC 5crh projectiles are based upon measurements of the incomplete APC 5crh shell bodies located at the Museum of Military History in Budapest and on estimates based upon war-time photographs of completed projectiles.
  • ^Unlike German guns of this caliber, all of the propellant for these Škoda guns was in a single brass cartridge.
  • ^This is an estimate based upon the larger chamber size of the K10.
  • ^A new propellant formulation was introduced shortly before the start of the war which was cooler burning and produced less smoke.
  • ^A sealer/pusher pad extended from the mouth of the cartridge by about 1.8 in (4.6 cm).
  • ^The MV for Italian service comes from a wartime German document. This reduction from Austro-Hungarian MV might have been the result of the use of Italian propellant in place of the original Austro-Hungarian propellant.
  • ^Outfit for the Radetzky class was 38 AP and 38 SAPC per gun. Nine projectiles were stored in the rear of each gunhouse, which also helped to balance the turret. There was actually space in the mounting for about 90 rounds, but they never carried this many. A Note on Sources: Friedman in "Naval Weapons of World War One" says 84 rounds per gun were carried but this seems to have double counted the ready rounds.
  • ^Outfit for Tegetthoff class was 38 AP and 38 SAPC per gun in magazines plus another six rounds per gun (18 total) in the in the rear of each gunhouse, which also helped to balance the turret. There was actually space in the mounting for about 100 rounds, but they never carried this many.
  • There are two 30.5 cm shell bodies on display in the yard of the Military History Institute and Museum, Budapest. See photograph below. These are incomplete 5crh types which lack AP caps and windshields, consisting of only the cast steel body. There is also a SAPC 2crh projectile on display at the Museum of Military History, Vienna. There are two projectiles said to be from Viribus Unitis at the Museo Nazionale Scienza e Tecnologia Leonardo da Vinci in central Milan, Italy.


Ranges with Austria-Hungary shells
Elevation 992 lbs. (450 kg) AP 2crh Shell 1,001 lbs. (454 kg) APC 5crh Shell
3.3 degrees --- 6,560 yards (6,000 m)
6.0 degrees --- 10,930 yards (10,000 m)
16.0 degrees 17,830 yards (16,300 m) 20,890 yards (19,100 m)
20 degrees 19,900 yards (18,200 m) about 24,000 yards (22,000 m)
  • Official range tables for the 30.5 cm shells went up to 15,000 m (16,400 yards).
  • When the Radetzky class switched from 2crh to 4.5crh projectiles their range increased from 18,500 meters (20,230 yards) up to 22,000 meters (24,060 yards).

Armor Penetration

Range 992 lbs. (450 kg) APC 2crh Shell
KC Armor
1,001 lbs. (454 kg) APC 5crh Shell
KC Armor
6,560 yards (6,000 m) --- 18.7 in (475 mm)
10,940 yards (10,000 m) --- 10.7 in (272 mm)
17,830 yards (16,300 m) 5.4 in (136 mm) ---
19,900 yards (18,200 m) 4.2 in (106 mm) ---
20,890 yards (19,100 m) --- 6.8 in (173 mm)

Data is from "Naval Weapons of World War One."

Range 992 lbs. (450 kg) APC 2crh Shell
KC Armor
1,001 lbs. (454 kg) APC 5crh Shell
KC Armor
5,470 yards (5,000 m) 17.1 in (433 mm) 19.8 in (502 mm)
10,940 yards (10,000 m) 8.0 in (202 mm) 10.7 in (273 mm)
16,400 yards (15,000 m) 5.6 in (143 mm) 8.2 in (208 mm)

Data is from "Austro-Hungarian Battleships and Battleship Designs: 1904-1914."

The acceptance requirement for the Zündergranate L/4 (SAPC) was to be able to penetrate a 180 mm (7") KC plate at a striking velocity of 540 mps (1,770 fps), equivalent to a range of 8,000 m (8,750 yards). Data is from "Austro-Hungarian Battleships and Battleship Designs: 1904-1914."

Mount/Turret Data

Designation Two-gun Turrets
   Radetzky (2)

Three-gun Turrets
   Tegetthoff (4) 1b

Weight 2b 3b Two-gun Turrets: 432 tons (439 mt)
Three-gun Turrets: 669-679 tons (680-690 mt)
Elevation 4b Radetzky: -4 / +20 degrees
Tegetthoff: -4 / +20 degrees
Elevation Rate 2.5 degrees per second
Train +140 / -140 degrees
Train Rate 3 degrees per second
Gun recoil 33.5 inches (85 cm)
Loading Angle +2 degrees
  • ^On the Tegetthoff class the heavy weight of the superimposed turrets caused hull distortions, requiring stiffening of the longitudinal frames.
  • ^The superimposed triple turrets were heavier than the lower turrets. Weights of individual turrets all differed slightly. For example, Turret III on Prinz Eugen was 687 tons.
  • ^Some references quote triple turret weights of 616-619 tons (626-629 mt). These are taken from the Škoda plans of October 1909 that used 25 cm turret armor. The actual turrets had 28 cm armor and were consequently much heavier.
  • ^The Radetzky class and Viribus Unitis could elevate all guns to 20 degrees either individually or when coupled together. The other ships in the Tegetthoff class were able to elevate all guns individually to -4 / +20 degrees, but when the guns were coupled together, the elevation range for the center gun was -3 / +15.5 degrees and the outer guns were limited to -4 / +16 degrees.
  • These turrets were poorly protected with thin armor. There was an unprotected slot between the gunhouse and the barbette - see sketch below. The cupolas for the rangefinders on the turret roofs were overly large. A hit on one of these could have peeled back the thin turret roof armor.
  • Many sources state that under battle conditions the gun houses could not be ventilated as the ventilation system sucked in the propellant gasses rather than expelling them. Some of these sources state that shutting down the ventilation would make the turrets uninhabitable after no more than 15 minutes. Recent research by Mihály Krámli throws doubt on these statements and says that the fresh air supplied by the ventilation system was probably adequate.
  • Projectiles were stored nose-down hanging by chains from the shell room overhead.

Additional Pictures


"Naval Weapons of World War Two" by John Campbell
"Naval Weapons of World War One" by Norman Friedman
"The Big Gun: Battleship Main Armament 1860-1945" by Peter Hodges
"The Viribus Unitis Class" article in "Warship Volume II" and "A's and A's" comments in "Warship Volume III" both by Friedrich Prasky
"A Szent István Csatahajó" [The battleship Szent István] by Balogh Tamás and Csepregi Oszkár
"Entwickelung des Schieß - und Artilleriewesens der k. u. k. Kriegsmarine in den letzten Jahren" [Development of the firing and artillery system of the k. u. k. Kriegsmarine in recent years] by kuk Marinetechnische Komitee (ca. 1912)
"Unterricht für die 30.5 cm und 24 cm Geschütz-türme - S.M. Schiffe Typ 'Radetzky'" (Genehmigt mit Eriaß P. K./M. S. Mr. 4243 ex 1912.) [Information for the 30.5 cm and 24 cm gun turrets on the S.M. Ship Type 'Radetzky']
Original research by Mihály Krámli, author of "A Használhatatlan Lövegtornony Mítosza: Legenda Vagy Valóság?" [The Myth of the Useless Turret: Legend or Reality?] and "Az Osztrák-Magyar Monarchia Csatahajói: 1904-1914" [Austro-Hungarian Battleships and Battleship Designs: 1904-1914] {Link - Hungarian to complete book in pdf form and Link - English}. Paperback copies, printed on A4 paper, are available. Contact NavWeaps by clicking on the Contact link above or below.
Email discussions with Mihály Krámli on 08-09 April 2023
Special help from Daniel Papp and András Hatala

External Sites

Page History

27 November 2007 - Benchmark
18 July 2010 - Updated with information supplied by Mihály Krámli
12 October 2013 - Added pictures of Radetzky turret and cartridge being rammed
01 May 2014 - Added additional gun, ammunition and mounting information, new range and armor penetration tables
20 November 2018 - Converted to HTML 5 format, reorganized notes, added propellant weight for non-K10 guns, added turret weights, added photograph of damaged guns
19 March 2019 - Added photographs of breech from exploded gun and Radetzky
07 April 2020 - Added ammunition data per research by Mihály Krámli and sketches by András Hatala
11 May 2020 - Modified note regarding turret oxygen supply, added sketch of gap between gunhouse and barbette
17 July 2020 - Corrected typographical error and added link to Mihály Krámli book
24 August 2020 - Updated propellant weight for K10
15 April 2021 - Added photographs of sailors loading 30.5 cm projectiles and SAP projectile
11 June 2021 - Minor edits
04 October 2021 - Added link to Mihály Krámli A-H Battleship book in English
14 October 2022 - Changed link about turret ventilation to point at History and Technology essay
12 April 2023 - Corrected descriptions of APC projectiles based upon new information from Mihály Krámli, added additional data to armor penetration tables, added photograph of Zrínyi
28 June 2023 - Added photograph of incomplete 30.5 cm APC at the Military History Institute and Museum, Budapest