Mine shell (projectile)
A mine shell (directly translated from the german term minengeschoß) is an shell type consisting of a very high-capacity high explosive shell. Originally an anti-fortification shell it is today mainly used for aircraft and anti-aircraft weaponry.
Effect, construction & useEdit
The mine shell is a more explosive version of the common high-explosive and high-explosive fragmentation shells, relying more on damage through the blast alone than the combination of blast and fragmentation. This is referred to in Swedish as tryckvågsverkan, meaning pressure wave damage. This effect is wanted when you want to blow big main holes in specific materials like concrete or aircraft skin. Tho achieve this effect mine shells features very thin shell walls which in turn allows more explosive filler at the cost of less fragmentation.
Beyond impact effect mine shells have different weight properties compared to regular high explosive shells. Explosive filler is lighter than metal which makes the projectiles a lot lighter which in turn gives them higher muzzle velocity compared to heavier shells and also less recoil. Some disadvantage of this though is reduced range as less weight leads to less momentum and the lower recoil can make mine shells problematic to use in recoil operated guns.
The word mine in the name mine-shell, although in English it's directly translated from the German word minengeschoß, does not refer to the modern use of the word, for example land mine and naval mine. Mine is an old (but still used) munition term from, among others, the weapons terminologis of Germany and Sweden. While the munition term "mine" in its original languages (German: minen, Swedish: min) differs from their respective words for land mines (German: mine, Swedish: mina) the munition term originates from the original meaning of the word mine which originally meant something along the lines of explosive ordnance, unlike the modern meaning of the word which is more defined.
The munition term itself (German: minenwirkung, Swedish: minverkan), which roughly translates to "mine power" or "mine effect", specifically means an explosive device, mainly a projectile, that damages its intended target with the power of the pressure wave created from the explosion.
Dedicated mine shells originates in Germanic countries such as Germany and Sweden with the earliest known type being for a Swedish 22 cm naval howitzer from 1878, although it’s very possible the type was used previous to this as the German and Swedish terminology system has its roots from the 1700's. The shell type was used in a lot of different types of high caliber cannons both on land and on water around the turn of the century before seeing a decline around world war one. It was probably decided that mine shells had a smaller field of use on the modern battlefield compared to the fairly similar high-explosive shell, therefore rendering the use of 2 similar shells obsolete.
German use of mine shells in world war twoEdit
During world war two mine shells would see a resurgence as the germans started to use the type in low caliber aircraft and anti-aircraft autocannons. Previous to this mine shells had only been constructed for high caliber cannons due to technical difficulties in creating lower caliber mine shells. The creation of mine shells requires casting as the walls of the shell has to be extremely thin. This was previously not possible so lower caliber explosive ammunition were created by drilling the explosive cavity into a solid steel shot, which limited how thin the walls of the shell could be which made it so even the most explosive low caliber shell types had to be classed as high-explosive shells (blast and fragmentation) as the thickness of the walls just limited the explosive capacity too much. While such shells did their job perfectly fine against ground targets they were more limited in anti-air use. During world war one, when planes were made out of wood and canvas, low caliber high-explosive shells worked perfect against air targets as their explosive and fragmentation effect tore the canvas on the planes to shreds. But during the 1930's, when planes started to be made out of metal, these types of shells started to be less effective as the fragments had insufficient effect on construction integrity or control surfaces compared to the actual explosion.
One of the first ones to take note of this and do something about it were the germans when they in the late 1930's had problematic trials with the 20 mm MG FF cannon. Its conventional high explosive rounds didn't have satisfactory results against aircraft in the manner as mentioned above. As a result of these trials, the German ministry of air defense "Reichsluftministerium", or "RLM" for short, ordered the development of mine shells for the 20 mm MG FF cannon in 1937. To make make mine shells in 20 mm caliber the German ordnance engineers had to try new methods of construction and designed a round made from high quality drawing steel which allowed the walls of the shell to be made thin enough. These new 20 mm mine shells where really successful and blew big holes in airplane skin which severely affected the airplanes structural integrity and performance. These rounds integrated into ammunition belts with other types of rounds like armor piercing incendiary made for some very effective and versatile ammunition belts.
Besides the improved damage output a property of mine shells became problematic for use in the 20 mm MG FF cannon. Due to the lightweight nature of mine shells the new 20 mm mine shells lacked the recoil needed to operate the 20 mm MG FF cannon. This required a modification of the recoil mechanism so the cannon could fire this new shell, but this in turn made it unsafe to fire the old ammunition. In the interest of avoiding such errors, the modified weapon was redesignated the 20 mm MG FF/M, M for Minengeschoß.
Once the properties of low caliber mine shells where fully understood the Luftwaffe found out they had potentially created a game changer as the recoil/velocity ratio made it possible to create very high caliber guns that would have low enough recoil to effectively be mounted on conventional aircraft but at the same time achieve useful velocities, not to mention the devastating effect such mine shells would have on aircraft. One of such weapon became the 30 mm MK 108 which became highly militarily significant during the second half of the war. Throughout the war the Germans would refine their mine shells by making them more streamlined to compensate the lost momentum from the light weight, albeit at the loss of a little explosives capacity. The streamlined mine shells for the 30 mm MK 108 where designated Ausf.C. and featured 72 grams of nitropenta (PETN), compared to the original blunt-nosed Auf.A which had 85 grams of PETN. (Note that the Auf.B was a training shell without explosives.)
To give some impression of the actual difference in payloads between mine shells and conventional high-explosive shells, the 20 mm mine shell used in MG 151/20 and MG-FF/M cannons had an 17 g HE filling while the typical filler load in conventional 20 mm shells for the MG-FF at the time was 4.5 to 6.5 Grams. British and American shells at the time had 10-12 grams.
Even in modern times some of these WW2 payloads are impressive as not even the PGU-13/B HEI round for the GAU-8/A Avenger gun of the A-10 Warthog or the 30 mm OFZ shell of Russian GSh-301 and GSh-30-6 cannons comes close to the German WW2 mine shells of the same caliber. 72-85 grams compared to 58 to 48,5 grams respectively for the PGU-13B and OFZ.
Germany first used Minengeschoß ammunition during the battle of Britain when MG FF/M armed Bf 109E's and Bf 110C's flew missions over from France to Britain. The 20 mm mine shell of the MG FF/M was soon adopted for the 15 mm MG 151 heavy machine gun in a new cartridge (20x82mm) as the original 15 mm cartridge proved too weak. These were subsequently named the MG 151/20 and became the Luftwaffe's standard 20 mm gun until the end of the war. The MG 151/20 proved to be one of the best 20 mm air-to-air guns of WW2 as it had a high fire rate coupled with good ballistics which coupled with the mine shells made for a great weapon against all sizes of aircraft.
After the defeat of Germany in World War II, several countries started using mine shells for their own post-war aircraft and anti-aircraft armament, for example in the HE shells of Britain's ADEN cannon and the French DEFA 540. The guns themselves were developments of the German Mauser MG 213.
Sweden having experience with the shell type from earlier developed several different mine shells in several different calibers after the war. Some examples being a mine shell variant for the 20 x 110 Hispano cartridge and one for the 57 x 230R Bofors cartridge.
- Lärobok i Militärteknik, vol. 4: Verkan och skydd.
- Nordisk familjebok.
- "22 cm mingranat för haubits fm/78".
- The type can be found in Swedish ammunition manuals for guns in caliber 75-150 mm around the years 1902-1914 disappearing from manuals after ww1 to the start of ww2.
- "Shell types: Minengeschoß".
- Williams and Gustin 2003
- Forsyth 1996, p. 168
- Note: The information in Forsyth 1996 is on the design and construction of the MK 108 and the relevant Minengeschoss.
- Beskrivning över 20 mm AKAN m/49. Stockholm: KFF förlag. 1955. Sweden. 1955.
- Flyghistorisk revy nummer 31, SAAB 18. Sweden: The Swedish air historical society. 1984. p. 76.
- "Gripens vapen (the weapons of the Griffon) pdf" (PDF).