A low-angle weapon intended for surface action, this gun armed all of the German destroyers built before the start of World War II and a few war-built ones. There were also twin mounts planned for the never-built Type XI U-boats (U-Kreuzer) and for an early design version of the Type 1936A (Mob) destroyers.

At least eight of these guns were exported to Greece for arming the destroyers of the Vasilevs Georgios class.

Early guns were bored-out versions of the 10.5 cm/55 (4.1") SK C/28. The production guns were constructed of a loose barrel, jacket and breech end piece with a vertical sliding breech block.

Some of these guns were still in service as of 2003 in coastal defense units in Norway.

All German 12.7 cm guns had an actual bore diameter of 12.8 cm (5.04 in).

• ^

  Guns designed for the Type XI U-Boats weighed 10,196 lbs. (4,625 kg) due to their increased breech end balance weights.
• ^

  The Type 24 torpedo boats Leopard and Luchs were used to test the prototypes of these weapons and had their 10.5 cm/55 guns replaced in 1932. Much information was gathered during these evaluations and the improved production version made its service debut in 1934.
• ^

  Converted 10.5 cm (4.1") SKC/28 guns weighed 7,848 lbs. (3,560 kg).
• ^

  This weapon was designed for a ROF of 18 - 20 rounds per minute, but the above figure was typical for well-trained crews. As these were open mounts, bad weather or Arctic conditions could greatly reduce the ROF.

• ^

  The sources below differ regarding the ammunition used for these weapons. For the most part, I have relied upon the data in M.Dv. Nr. 170,27 and in "German Destroyers of World War Two."
• ^

  Actual German designations

  HE L/4,4 nose fuze	12,7 cm Spgr. L/4,4 Kz (m.Hb)
  HE L/4,4 nose fuze AA	12,7 cm Spgr. L/4,4 Kz (m.Hb) – Haube abgeschraubt [unscrewed cap]
  HE L/4 base fuze	12,7 cm Spgr. L/4 Bdz (m.Hb)
  Illumination L/4,5	12,7 cm Lg L/4,5

• ^

  There were two versions of the HE L/4,4 nose fuze projectile, these having minor differences in the fuze packaging and very slight differences in the burster weight.
• ^

  The AA projectile was the same as the standard HE Nose projectile, but had a time fuze in place of the instantaneous impact fuze and did not use the ballistic cap (windshield). This AA projectile was similar to that for the 15 cm/60 (5.9") SK C/25, see Anti-Aircraft Projectiles on that datapage for a sketch.
• ^

  The HE L/4 base fuze projectile appears to have been designed sometime in 1944 or early 1945 and details for it are few. It is not known if it actually entered service use. "Naval Weapons of World War Two" states that these were issued to destroyers, but I have found no other source to corroborate that claim.
• ^

  Burster weights (G = Gesamtgewicht and S = reiner Sprengstoff) and compositions from M.Dv. Nr. 198 which gives two different sets of weights for the nose fuze projectile. This is related to the way that the bursters were packaged in the cavity. Both weights are included here for reference.
• ^7.17.2

  The bursters of the HE nose fuze and nose fuze AA projectiles were made entirely with Fp 1.
• ^

  The burster for the HE L/4 base fuze projectile was made from Fp 1, Fp 15 and Fp 20. Burster weights shown above are my estimates.
• ^

  The cartridge rim diameter was 160.2 mm.
• ^

  Outfits for destroyers were HE nose fuze with and without tracer and 80 illumination rounds per ship.
• Nose fuzed HE was 8.6crh.
• Exercise and practice rounds were produced for this weapon.
• Nammo Raufoss produced an anti-ship projectile (ASP M88) starting in 1989. This projectile had the same interior and external ballistics as the earlier German 12.7 cm rounds and was essentially a scaled up version of the ASP M85 used for former German 10.5 cm/45 (4.1") guns. The projectile weighed 61.7 lbs. (28.0 kg) and had a bursting charge of 7.0 lbs. (3.2 kg).

German naval guns during World War II between 12.7 cm and 40.6 cm were issued HE Nose Fuze projectiles that had ballistic caps [Spgr. Kz (m.Hb)]. Similarly, older naval guns now used in Coastal Defense Batteries were issued new HE Base and Nose fuzed projectiles with ballistic caps [Spgr. Bdz u. Kz (m.Hb)]. As can be seen in the sketch below, these projectiles had the impact fuze located on the head of the projectile body, not on the head of the projectile. While this approach improved and simplified the connection between the fuze and the burster, this design had a weakness in that the ballistic cap actually "protected" the fuze when the shell made a glancing blow on the target instead of a direct hit. If the fuze was not crushed from this kind of hit, then the shell would not detonate.

What the Germans did to improve the likelihood of detonation when the projectile made only a glancing hit was to insert a wooden rod, called the Stößel ("Ram") in these sketches, between the nose of the ballistic cap and the fuze. With this design, if the ballistic cap struck something hard enough to deform the cap, even if not a direct hit, then the rod would still be pushed into the fuze and initiate the detonation. Finally, in case of a highly oblique or "grazing" impact, the fuze was designed such that inertia would force the firing pin and primer holder together and still initiate the fuze detonation even if the rod was not pushed into the fuze.

For most projectiles with ballistic caps, the Stößel was placed sideways inside the cap during storage and transport so as to prevent damage. At least one projectile, the 24 cm Spgr. L/4,2 Bdz u. Kz (m.Hb) nA, was a later "New Art" design that did not need the Stößel moved from its ready position.

In regards to this German design, it should be noted that the 16" (40.6 cm) Mark I guns used on the HMS Nelson class battleships used similar HE projectiles with ballistic caps that had the fuze on the nose of the projectile body and not on the nose of the cap. However, unlike the German design, these lacked any connection between the fuze and the nose of the ballistic cap. HMS Rodney found during her bombardment of Oran in November 1942 that many of these projectiles failed to explode and they were withdrawn from service in 1943. A new HE projectile was issued later and this had a true nose fuze and was of better ballistic shape.

• ^

  The MPL C/28 mountings were converted from 10.5 cm mountings.
• ^

  None of the twin mounts actually made it past the design stage. They do not appear to have had the guns individually sleeved.
• Gun Shield Thickness:
      MPL C/28: 0.197 in (5 mm)
      MPL C/34: 0.315 in (8 mm)
      U.DrhL C/38: 0.787 in (20 - 30 mm)
      DrhL C/38: 0.787 in (20 - 30 mm)

"Naval Weapons of World War Two" by John Campbell
"Jane's Ammunition Handbook: Ninth Edition 2000-2001" edited by Terry J. Gander and Charles Q. Cutshaw
"German Warships 1815-1945" by Erich Gröner
"The German Navy in World War II" by Robert Jackson
"Die Geschichte der deutschen Schiffsartillerie" by Paul Schmalenbach
"German Naval Guns: 1939 - 1945" by Miroslaw Skwiot
"German Warships of World War II" by J.C. Taylor
"German Destroyers of World War Two (2nd Edition)" and "Destroyers of World War Two: An International Encyclopedia" both by M.J. Whitley
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"Merkbuch: über die Munition für die 12,7cm SKC/34 in 10,5cm MPL C/28 und 12,7cm MPL C/34" M.Dv. Nr. 170,27 by Oberkommando der Kriegsmarine
"Munitionsvorschriften für die Kriegsmarine - Panzersprenggranaten mit Haube - a) Psgr (m.Hb)" M.Dv. Nr. 190,1A1 by Oberkommando der Kriegsmarine
"Munitionsvorschriften für die Kriegsmarine - Hülsenkartusche" M.Dv. Nr. 190,4A1 by Oberkommando der Kriegsmarine
"Übersicht über die für die Marinegeschütze und deren Abk K zu verwendende Munition und ihre Einzelteile einschließlich Salut- und Manöverladungen" M.Dv. Nr. 198 by Oberkommando der Kriegsmarine
"Hauptsächliche Angaben über an Bord Befindliche Geschütze für das Handbuch für Admiralstabsoffiziere" dated 1/1/1939 by Oberkommando der Kriegsmarine
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Special help from Tony Williams, Bene Adler and Thorsten Wahl

14 October 2008 - Benchmark
05 June 2011 - Minor additions
12 February 2014 - Changed burster weights
09 March 2019 - Converted to HTML 5 format, reorganized notes, added section on HE Nose Fuze with ballistic caps and added ammunition information and sketches from M.Dv. Nr. 170,27, M.Dv. Nr. 190,1A1 and M.Dv. Nr. 190,4A1
25 August 2019 - Added link to AA Projectile section
18 April 2021 - Corrected typographical error
14 December 2022 - Corrected typographical error, minor formatting changes
29 March 2024 - Added photograph of fuzes
28 August 2024 - Added burster notes and propellant information
24 December 2024 - Added sketch of 12,7 cm Spgr. L/4,4 Kz (m.Hb)
01 March 2025 - Minor changes
16 April 2025 - Added data on 12,7 cm Spgr. Bdz (m.Hb)
16 June 2025 - Redid Burster table
05 November 2025 - Added details of twin mounts