Röchling shell
{{Short description|Bunker-busting artillery shell}}
File:Bundesarchiv N 1603 Bild-117, Russland, Sewastopol, zerstörte Festung Maxim Gorki.jpg
Röchling shells were bunker-busting artillery shells, developed by German engineer August Coenders during World War II, based on the theory of increasing the sectional density to improve penetration.{{cite book|title=Waffen Revue|year=1988|volume=72|language=de|chapter=Das Röchling-geschoss|pages=73–106}}
Description
The subcaliber shells made from chrome-vanadium steel were able to penetrate much more than {{convert|4|m|ft}} of reinforced concrete roof before burying the shell through the floor and into earth.{{Cite book|url=https://books.google.com/books?id=KAYhAQAAIAAJ|title=Hitler's Miracle Weapons: The Secret History of the Rockets and Flying Crafts of the Third Reich Volume 2 - from the V-1 to the A-9; Unconventional Short- and Medium-Range Weapons|last=Georg|first=Friedrich|date=2005|publisher=Helion Limited|isbn=9781874622628|pages=212|language=en}} They resembled fin-stabilized arrow shells, but had a discarding flange acting as a driving band instead of fins.{{cite book|author1=Basil T. Fedoroff|author2=Henry A. Aaronson |author3=Earl F. Reese|author4=George D. Clift|title=Dictionary of explosives, ammunition and weapons (German section)|chapter=Röchling Anticoncrete Projectile|chapter-url=https://archive.org/details/DTIC_AD0160636/page/n169|page=Ger 160|publisher=Picatinny Arsenal|date=July 7, 1958|doi=10.21236/ad0160636}} Despite high penetration, these shells had a low muzzle velocity, and thus a high dispersion, {{convert|36|m|abbr=on}} on {{convert|1000|m|abbr=on}} range. As a result, they saw very limited use during World War II; only about 200 shells were ever fired even though 6,000 such shells were made for the very large howitzers like the 21 cm mortar.{{citation needed|date=April 2018}}
Röchling shells were developed for the 21 cm Mörser 18, a captured French 34 cm railway gun 674(f), and the 35.5 cm Haubitze M1 only. In addition, many experimental HE shells were made for the 3.7 cm Pak 36 and 5 cm Pak 38 anti-tank guns.{{Cite web|url=http://www.balsi.de/Weltkrieg/Waffen/Sonderwaffen/Heer/roechlingranaten.htm|title=Die Roechlingranaten des Heeres|website=www.balsi.de|access-date=2016-08-03}}
Use
File:Röchling shell impact in Fort d'Aubin-Neufchâteau.jpg
Röchling shells were tested in 1942 and 1943 first against the Belgian Fort de Battice then against the Belgian Fort d'Aubin-Neufchâteau.{{Cite web|url=http://html2.free.fr/canons/flech.htm|title=Premier obus flêchette|date=30 December 2012|website=Les Canons de l'Apocalypse|language=fr|access-date=2016-08-03}}{{cite web|url=http://derelicta.pagesperso-orange.fr/aubin3.htm|title= Les étranges obus du fort de Neufchâteau|language=fr|work=Reliques:souterrains et industries|last=Delacruz|first=Jean-Paul }} They were also tested against the fortresses of Hůrka,{{Cite web|url=https://www.flickr.com/photos/theadventurouseye/15158381525/|title=Artillery fort Hůrka – Röchling projectile embedded into the wall|website=Flickr|date=23 August 2014 |access-date=2016-08-03}} Hanička and Dobrošov{{Cite web|url=http://www.bunkry.cz/clanek.aspx?id=1256|title=Bunkry.cz – Protibetonové Granáty Röchling|last=Čermák|first=Ladislav|website=www.bunkry.cz|access-date=2016-08-03}}{{Cite web|url=http://www.bunkry.cz/clanek.aspx?id=1216|title=Bunkry.cz – Dělostřelecká tvrz Dobrošov|last=Čermák|first=Ladislav|website=www.bunkry.cz|access-date=2016-08-03}} (today's Czech Republic),{{Cite journal|last1=Jiricek|first1=Pavel|last2=Foglar|first2=Marek|date=2015-01-01|title=Numerical simulation of the effect of regular and sub-caliber projectiles on military bunkers|journal=EPJ Web of Conferences|language=en|volume=94|page=04049 |doi=10.1051/epjconf/20159404049|issn=2100-014X|doi-access=free}} the Gössler wall, Toplitzsee (Austria) and at the Hillersleben test facility (Germany).
They were regarded as a German secret weapon, and there is speculation that their use was limited in order to reduce the chance of dud shells being recovered and exploited by the Allied forces.{{Cite book|url=https://books.google.com/books?id=TQ0tAQAAIAAJ|title=Encyclopedia of World War II|last=Keegan|first=John|date=1990|publisher=Gallery Books|isbn=97-80831753504|page=212|language=en}} A more likely reason, however, is their poor accuracy.{{cite web|author=War and Games |title=V 3 – THE HIGH-PRESSURE PUMP GUN |url=http://warandgame.wordpress.com/2009/07/13/v-3-the-high-pressure-pump-gun/ |access-date=2009-12-15 |url-status=dead |archive-url=https://web.archive.org/web/20090723072338/http://warandgame.wordpress.com/2009/07/13/v-3-the-high-pressure-pump-gun/ |archive-date=July 23, 2009 }}
Preserved small-size fin-stabilized prototype of Röchling shell (36 cm long) is since 2020 exhibited in the Museum of Czechoslovakian fortifications,[http://hurka.boudamuseum.com/en/index.php Museum of Czechoslovakian fortifications] (en) inside the {{ill|fort Hůrka|cs|Hůrka (dělostřelecká tvrz)}}. Remnants of full-sized test shells are still visible in the walls of the fort.{{Cite news|url=https://www.irozhlas.cz/veda-technologie/historie/tvrz-hurka-muzeum-strela-prototyp-zbran-naciste_2007201235_tzr|author=Josef Ženatý |title=Na tvrzi Hůrka mají světový unikát. Vojenské muzeum vystavuje prototyp tajné nacistické zbraně|trans-title=The Hůrka Fortress is a world unique. Military Museum exhibits a prototype of a secret Nazi weapon|lang=cs|date=July 20, 2020|newspaper=iROZHLAS}}