Now you've got me started on 120mm ammunition. Here is the full range of ammunition for the L11 gun:
Firstly the armour penetrators, high velocity rounds which rely on kinetic energy to penetrate armour.
From the left, APDS (armour piercing, discarding sabot), DS(P), Discarding Sabot (Practice) and a drill round for loading simulators.
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On this you can see the penetrator on my post above:
APDS was replaced with the introduction of the L11 A5 gun with the even more effective fin round - APFSDS (armour piercing fin stabilised and you know the rest).
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And then the dual purpose rounds. UK has been unique post war in sticking to the rifled gun, for two reasons. Firstly rifled tends to be more accurate but perhaps more importantly, you need rifling to fire low velocity high explosive. The UK recognised the threat from infantry anti-tank guided weapons, particularly after the mauling the Israelis took from SAGGER. To defeat ATGW crews, you needed artillery but if that wasn't available, the UK doctrine was to give tank crews their own HE capability. Hence the HESH round - High Explosive Squash Head. This is a dual purpose round, which is capable of defeating significant thickness of armour. The round compacts like a cow pat when it hits armour and the base fuze then explodes the charge. The round works by setting up shock waves through the armour, which knocks off large scabs inside, to the detriment of the enemy crew. It is also a very effective HE round.
Other nations favoured HEAT (high explosive anti-tank), which forms a jet of molten metal to penetrate armour. This can easily be defeated by spaced armour or explosive reactive armour. For that reason, UK traditional favoured rifled guns firing HESH. I think this was the right policy. I see now though that the Challenger 2 upgrade will have a smooth bore gun, I suspect because interoperability with other nations trumps effectiveness.
There was also a very effective smoke round which we used both to obscure and to mark targets.
In this photo, L-R, you have HESH, 120 Smoke and SH(P) (squash head practice, the inert training round):
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Finally, the charge. Chieftain was again unique in another respect. The UK drew lessons from the WW2 loss of tanks from ammunition explosions when penetrated. Traditional brass cased single piece ammunition is notoriously combustible in a turret fire. Chieftain overcame this vulnerability by using separated ammunition, in which the propellant was encased in cloth or a composite material and stored, crucially, below the turret ring in wet lined charge bins, so that if the turret was penetrated, the wet liners of the charge bins would disrupt and protect the charges from detonation. If you see film of Russian T-72 going up in Syria, you'll see the devastating effect of ammunition fires. Abrahms and later Russian tanks store ammunition in the turret and it makes them vulnerable. The designers of Abrahms were so worried by it that they provided armoured shutters which are supposed to close off the ammunition in the turret bustle, which would then blow off, separating the ammunition from the crew....... Detractors claim that separated charge ammunition is slower to load. That's rubbish. With a well trained crew, we could get six rounds off in a minute. With CR2, the gun returns to a loading position after each round and is even faster. And manual loading doesn't break down or try to load the loader's arm into the breech as do some autoloaders.
The bag charges were pretty inert. In the breech, they burnt rather than exploded. It was possible to remove the combustible rods and break them up. I'm told they could then be ignited to produce a very satisfactory nighttime fire to keep warm......not that there were spare bag charges around.
The other significant advantage of separated ammunition is that you don't get a smoking, large, hot, heavy shell case back into the turret, taking up room and suffocating the crew. With the British L11, the charge is ignited by a vent tube, a cartridge case the size of a .50" round, loaded in a magazine below the breech. That's all that you get back into the turret. No fumes either.
The charge for Sabot/fin, is twice the size as the charge for the lower velocity HESH and smoke rounds:
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Hope that's of interest. Anyone going to make some rounds?
