30.5 cm MRK L/22

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30.5 cm MRK L/22
30.5 cm MRK L/22 on ship carriage
Type
Place of originGermany
Service history
Used by
Production history
DesignerKrupp
Designed1876
ManufacturerKrupp
Produced1876
Specifications
Mass
  • RK: 36,600 kg[1]
  • MRK: 35,600 kg[2]
Length6,700 mm[3]
Caliber305 mm[3]
Breechhorizontal sliding wedge
Muzzle velocity
  • 488 m/s as first used[4]
  • 522 m/s in the 1880s.[5]

The 30.5 cm Mantel Ring Kanone L/22 was a 30.5 cm 22 caliber long Krupp Mantel Ring Kanone. It was a rifled breech loader built-up gun with a Krupp cylindroprismatic sliding breech. It was a further development of the earlier 30.5 cm Ring Kanone L/22 that Krupp had developed and exhibited at the 1873 Vienna World's Fair.

RK vs MRK[edit]

Krupp hooped (RK) vs. jacketed and hooped (MRK)

There were two types of Krupp 30.5 cm guns of 22 caliber length. The earliest was a Ring Kanone (RK), it was succeeded by a Mantel Ring Kanone (MRK). Both had a built-up gun gun barrel. The older Ring Kanone (RK) construction, consisted of an inner tube and one or more layers of hoops (Ringe). In English, it was also referred to as a hooped gun. The later Mantel Ring Kanone (MRK) construction was also known as jacketed and hooped. It consisted of a thin inner tube that was surrounded by a thick jacket Mantel which contained the wedge slot, the jacket was again surrounded by the layers of hoops.[6]

30.5 cm RK L/22[edit]

Background: Heavier armor on ships[edit]

In mid 1872 and in May 1873 Germany held trials with its heaviest gun, the 28 cm RK L/22.[7] In an August 1873 note about the May 1873 trials, the artillery test commission noted that the 28 cm gun would not be strong enough in the near future. Some new ships had armor belts of 305 mm thickness with a supporting layer that was even stronger than the 18 in (457 mm) of teak found on Warrior. Other ships like Petr Veliky and a new British class were partly protected by 355 mm armor. These developments meant that in order to assure the superiority of the coastal artillery over ship armor, a heavier caliber than 28 cm was necessary.[8]

The Vienna 30.5 cm RK L/22[edit]

30.5 cm RK L/22 in 1873
The 30.5 cm RK L/22 as showpiece on the Vienna fair
Sketch of the RK L/22

Meanwhile, the Krupp steelworks happened to have made a heavier gun, the 30.5 cm Ring Kanone L/22.[9] Krupp initially made two of these guns. One was a showpiece of the Krupp pavilion on the 1 May to 31 October 1873 Vienna World's Fair.[10] The other gun was used for testing.[11]

The 30.5 cm L/22 gun got extensive media coverage by its appearance on the Vienna fair. It was made according to the Ring Kanone system. It consisted of an inner tube and three rings put on top of each other. One of the rings included the trunnions. Total length was 6,7 m or 22 calibers. The length of bore was 5.77 m. The gun had 72 parallel grooves with a twist length of 21.79 m. The grooves were 8.8 mm wide, the lands 4.5 mm wide. The total weight was 36,600 kg (i.e. 36 ton [1]). Charges were 50 or 60 kg of prismatic gunpowder.[10] The report of the test gave some further details.[1]

The Vienna gun was exhibited on a coastal carriage. The total carriage weight was 21,000 kg. A conspicuous feature of the gun and carriage was that they were so well balanced. From a physical perspective, two men could operate the gun. However, for an efficient rate of fire, about 10 men were needed. At the time, it was noted that Krupp had pro-actively developed the gun to counter prospective advances in ship armor.[10]

Prussia considers the 30.5 cm RK L/22[edit]

In February 1874 the German government appointed a commission to investigate the situation on the North Sea and Baltic coast. The commission concluded that for the North Sea a heavier caliber gun than 28 cm was not necessary for most places and not enough in other places. On the Baltic coast, it found that a heavier gun could be useful, but that it was probably more efficient to invest in torpedoes and monitors.[12]

In 1874 the German Admiralty considered the possibility of arming the projected Ausfallschiffe (small battleships for home waters) with the 30.5 cm Ring Kanone that Krupp had made in 1873.[13] In 1874 Prussia then ordered three 30.5 cm RK L/22 at Krupp.[14] Krupp offered the gun for a test that took place on 7 July 1875.[13] When fired with 65 kg of prismatic pulver it proved quite powerful, propelling a 305 kg shot to about 460 m/s.[15]

Labels of the 30.5 cm L/22 guns[edit]

Krupp referred to the Ring Kanone predecessor of our 30.5 cm MRK L/22 gun as the 'Lange 30.5 cm Kanone' (see 30.5 cm RK L/22 in 1873 pic). When the German navy took our Mantel Ring Kanone 30.5 cm L/22 into use, it had only one kind of 30.5 cm gun, and so it simply named it the '30.5 cm Kanone'. When in 1885, the navy changed its naming system to include the length of its guns in calibers, this became the '30.5 cm Kanone L/22'.[16] The two 'Vienna' guns did not get an official label, because they were not adopted for service. If they had been, their label would probably have become 30.5 cm RK L/22 in 1885.

The early 30.5 cm MRK L/22[edit]

The first 30.5 cm MRK L/22 is ordered[edit]

The armored gunboat SMS Natter (1880) of the Wespe class was armed with the 30.5 cm L/22

In August 1876 the Admiralty ordered that the projected armored gunboats would each be armed with a single 30.5 cm gun. It urged the artillery test commission to take a decision on the final inner construction (i.e. the rifling) of the gun. The artillery test commission proposed 60 or even better, 72 grooves of 2 mm depth, a twist length 45 caliber, a diameter of the powder chamber of 313 mm, a diameter of the rifled shot chamber 307 mm in the lands and 309 mm in the grooves, and a standard charge of 75 kg of prismatic gunpowder c/75.[17]

In 1875 Krupp had started to apply the new Mantel Ring Kanone construction for guns. This consisted of first placing a mantle over the inner tube before applying the rings. This made for an even stronger gun barrel than the Ring Kanone.[18] It also led to the MRK abbreviation for Mantel Ring Kanone. In view of the proposed charge of 75 kg of prismatic gunpowder, the artillery test commission already took the MRK construction into account when it made its proposal for the new 30.5 cm gun. In November 1876 the admiralty then ordered a 30.5 cm MRK.[17]

The probably dispappointing tests[edit]

The new 30.5 cm Mantel Ring Kanone was then tested. The results were probably disappointing. In a preliminary test, it was found that the atmospheric pressure inside the gun was higher than expected, already at a charge of 72 kg. At that charge, a kg of gunpowder had 1,030 cm3 of space to explode and atmospheric pressure rose to about 3,000 Atm, while Krupp stated that 3,500 Atm was allowed. In later tests the breech was repeatedly damaged by the high pressures, even after it had been reinforced. In these tests, the atmospheric pressures at 72 kg proved much higher than had been measured in the preliminary test.[17]

A new stronger breech was introduced and the gun was test-fired till the fall of 1878. Charges were from 72 till 74.5 kg, which resulted in average pressures of 3,200 to 3,400 Atm, dangerously close to the maximum pressure. Six shot burst inside the barrel. After 119 shots, barrel and breech had not suffered significant damage. The commission that tested the gun was not satisfied. It noted that with the measured pressures, the only option for the charge was to use the less explosive gunpowder that had been used in the tests. One of its members voiced his opinion that the powder chamber should be widened for an explosive charge of 78–80 kg with a space of 1,200 cm3 per kg and a maximum pressure of 2,800 Atm.[17]

Tests on board Wespe[edit]

In early 1877, the 30.5 cm Kanone L/22 was placed on board SMS Wespe. The gun weighed 36,729 kg, its carriage 25,000 kg. It was noted to be as powerful as the British 80 ton gun, but more accurate. Wespe would perform shooting trials with the 30.5 cm gun. If these were positive for the ship, there were plans to arm her with a 32 cm gun.[19]

The 30.5 cm MRK L/22 of 1878[edit]

The first Wespe class armored gunboat was launched in 1876, and the last was launched in 1881. We know that in 1878, there was actually a 30.5 cm Krupp gun in German service.[5] Therefore, there can be little doubt that a design identical or very similar to the first 30.5 cm MRK L/22 was adopted to arm the Wespe class. This is confirmed by an 1889 statement that the 30.5 cm MRK L/22 was designed in about 1876.[20]

In its early configuration, the 30.5 cm MRK L/22, was mentioned as 'Deutsche 30.5 cm Mantel Ringkanone. The gun was 6,700 mm or 22 calibers long. It weighed 35,600 kg. It fired a shot of 325 kg by using an explosive charge of 72 kg. Initial velocity was 488 m/s.[4] This is all in line with the data about the tests of the 30.5 cm MRK L/22 prototype.

The final 30.5 cm MRK L/22[edit]

Improvements in gunpowder[edit]

In order to reduce the strain on gun barrels, there were consistent and successful attempts to produce slower burning gun-powder. At first the Ring Kanone used prismatic gunpowder. Other types were Pellet- and Pebble gunpowder.[21] The original prismatic gunpowder C/68 was first replaced by the denser prismatic gunpowder C/75, which burned slower.[22]

When the C/75 powder was used, the difference with the older RK firing with C/68 powder became more marked. With 72 kg of C/75, the MRK fired a 367.3 kg shot with a speed of 488 m/s, as opposed to 60 kg for a 296 kg shot at a speed of 488 m/s for the older RK. The weight difference was then given as 36.6t for the RK vs. 35.6t for the MRK.[23]1881

In turn the gunpwoder C/75 was replaced by the even slower burning brown prismatic gunpowder C/82. This gunpowder made for an increased velocity if longer barrels were used, but also allowed increased velocity or heavier projectiles by using higher explosive charges.[22] The smokeless Würfelpulver C/89 was even more powerful.[24]

Final characteristics of the 30.5 cm MRK L/22[edit]

In 1889, the 30.5 cm MRK L/22 was specifically mentioned as a gun actually having been in service in 1878.[25] In 1896 it weighed 36 tons, including a breech piece of 1,340 kg. The carriage weighed 21,700 kg. The length of bore was 5,770 mm or L/18.9, which is in line with the 1878 situation. The 4,619 mm long rifled part was shorter than the earlier 4,750 mm long rifled part.[26]

The most profound change was that the explosive charge was now 202.8 lb or 92 kg of prismaic pulver C/82, and the shot weighed 725 lb/329 kg. Muzzle velocity was reported as 1,712 feet or 522 m/s.[5][26]

Further development[edit]

The 30.5 cm MRK L/25 at first seems to have been designed by simply making the L/22 a bit longer. It did not attract many customers. The 30.5 cm MRK L/35 was far more successful. It was part of a series of Krupp guns that introduced much longer barrels and longer projectiles. This was needed to fully profit from the concept of using an even higher charge of even slower-burning gunpowder, leading to a far higher muzzle velocity.[22] This concept was introduced when the few L/25's that were on order were not yet ready, and so these were changed to also use an increased charge and longer projectiles. As this was successful, it seems likely that the L22 was also changed to profit from slow-burning gunpowder.

Usage[edit]

German Navy[edit]

In the German Navy, the 30.5 cm MRK L/22 was used to arm the 11 armored gunboats of the Wespe-class gunboats. Even in the late 1890s, it was marked as the strongest gun of the German navy.[27] This was true for the weight of the shot, but the longer 28 cm guns were definitely more powerful.

Danish Navy[edit]

In the Danish Navy, the 30.5 cm MRK L/22 was used on board HDMS Helgoland.

Notes[edit]

  1. ^ a b c Galster 1873, p. 274.
  2. ^ Bode 1881, p. 88.
  3. ^ a b Von Müller 1879, p. 288.
  4. ^ a b Holzner 1883, p. 427.
  5. ^ a b c Vreeland 1889, p. 143.
  6. ^ Manual 1880, p. 49.
  7. ^ Von Müller 1879, p. 97.
  8. ^ Von Müller 1879, p. 172.
  9. ^ Von Müller 1879, p. 173.
  10. ^ a b c A-n 1874, p. 26.
  11. ^ A-n 1874, p. 27.
  12. ^ Von Müller 1879, p. 174.
  13. ^ a b Von Müller 1879, p. 260.
  14. ^ Krupp AG 1875, p. 49.
  15. ^ Von Müller 1879, p. 340.
  16. ^ Marineverordnungsblatt 1885, p. 2.
  17. ^ a b c d Von Müller 1879, p. 261.
  18. ^ Von Müller 1879, p. 259.
  19. ^ Hausschatz 1877, p. 496.
  20. ^ Vreeland 1889, p. 145.
  21. ^ Schott 1898, p. 870.
  22. ^ a b c Schott 1898, p. 871.
  23. ^ Waffenschmied 1885, p. 69.
  24. ^ Schott 1898, p. 872.
  25. ^ Vreeland 1889, p. 143,145.
  26. ^ a b Hartmann 1896, p. 952.
  27. ^ Zimmermann 1889, p. 64.

References[edit]

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