Mine shell

[4] This effect is desirable when attacking non-reinforced materials such as brick, concrete or aircraft skin, as these are relatively brittle and easy to penetrate and therefore do not need to be tackled with heavy, hard projectiles, but are tough enough to maintain their structure despite being pierced by shellfire and fragmentation.

The larger explosions generated by mine shells are more efficient at inflicting damage on such targets than the greater kinetic impact but smaller detonations delivered by conventional rounds.

This eventually led to mine-ordnance being defined as "contained explosions", which is alluded to in the name mine shell as its original purpose was to penetrate into fortification walls and burst inside.

[8] The historical equivalent English military term is High-Explosive, High-Capacity,[1][3] abbreviated as HEHC,[2] which has become uncommon or obsolete in modern times.

[16] Interestingly, mine-rockets developed in Sweden after WW2 were named sprängraketer (high-explosive rockets), even though their initial design was directly based on the German R4M.

[11] Mine shells were used in a lot of different types of high caliber cannons, howitzers, and mortars on both land and on water around the turn of the century, before seeing a decline after World War I.

During World War II, mine shells would see a resurgence as the Germans started to use the type in small caliber (initially 20 mm) automatic weapons, both to arm the Luftwaffe's fighter aircraft and for Flak.

As a result of these trials, the German air ministry, the Reichsluftfahrtministerium, or RLM for short, ordered the development of mine shells for the 20 mm MG FF cannon in 1937.

Although the shells themselves proved deadly, the guns had a poor rate of fire, relatively sluggish muzzle velocity and an inadequate magazine ammunition feed, and were soon to be replaced by the belt-fed MG 151.

This new type was originally introduced as a Minengeschoß-firing heavy machine gun, in 15 mm; but then it was realised that the earlier cannon-sized mine shells were more effective, and so a new larger cartridge (20x82mm) was created for the weapon.

The adapted gun, (more precisely designated the MG 151/20), became the Luftwaffe's standard 20 mm autocannon until the end of the war,[19] and with its high fire rate coupled with good ballistics and high-explosives payload for its caliber was overall among the best aircraft armament of the conflict.

One such weapon was the 30 mm (1.18 in) MK 108 which became highly militarily significant during the second half of the war, when the Allies began to mount their enormous bombing onslaught on German cities.

So large was the increase in internal volume indeed that it proved worthwhile to the Germans to refine these projectiles by making them more streamlined, sacrificing a little of this capacity, but thus partly compensating for the lower momentum characteristic of the Minengeschoß design.

Interestingly Germany already manufactured mine shells in caliber 50 mm (1.97 in) for guns like the 5 cm FlaK 41, but these only had an explosive charge capacity of 360 grams (0.794 pounds).

[16] These rockets were fitted to several German aircraft at the end of the war, most notably the Me 262, which used them to great effect during their limited service life.