Sir John Valentine Carden Survives. Part 2.

Have added it
What I mean was, I'm not seeing a ling between failed Italian HEAT and the British developing HESH.

Independent. Burney started his method to destroy thick concrete, not spall armor plate
I figured as much.

Functionality yes but to use the shell as a guide to how the gun came to be is kind of a stretch, particularly when looking at the 77mm HV. The barrel, Breach and recoil mechanism were all carried over almost entirely unchanged from the 75mm HV.

I will admit it can be a bit murky at times, the QF 75mm being a prime example. Is it as has been often claimed simply a bored out 6 pounder or is it a new build barrel mated to the breach and recoil mechanism of the 6 pounder? How then do you trace the liniage of that gun, is it a modified 6 pounder as often claimed or is it in essence a modified 75mm in British service?
Fair.
 
27 November 1941. Rome, Italy.

The last message from General Nasi was passed on to Benito Mussolini. The commander of the last Italian garrison in Africa Orientale Italiana (AOI Italian East Africa) reported that his last reserves had been unable to stop the enemy, and that armoured vehicles had entered the town. Coupled with the latest messages from Tripoli of British breakthroughs in the last defensive positions protecting the capital of Africa Settentrionale Italiana (ASI Italian North Africa) brought the reality of the loss of the Italian empire home to the Italian dictator.

While he would claim some credit for the defeat of Greece, in reality, without German help, he could have ended up losing Albania. His outrage at the inability to defeat the British by land, sea or air had left him at odds with his military command. The reminder that they had been planning for war beginning in 1942, not early 1940, was an affront to his judgement. He was terribly aware that there were plenty of people whose husbands and sons, brothers and uncles now were sitting in camps around the British empire. At least they knew they were safe, there were far too many grieving parents, widows and children. Resentment against the war, with only defeat after defeat, was also, to Mussolini’s mind, resentment towards himself. The support of the Blackshirts was assured, but the armed forces were a different kettle of fish. He would need to look after his own position now: he’d lost an empire, it wouldn’t take too much for him to lose power altogether.

Mussolini’s relationship with Adolf Hitler had also cooled dramatically. Despite sending an Infantry and Panzer Division to stiffen Italian resolve, the Italian army had failed completely, costing Germany those two Divisions. The fact that most of the defeats inflicted on the Italian forces of AOI had come from Indians and Africans, not Europeans, just confirmed Hitler’s disdain for his ally’s ability.

Berlin was now having to look at contingencies for the possibilities of various actions by the British. If they take on the remaining French possessions in Africa, especially on the Mediterranean coast, that would have consequences for the Petain regime in Vichy. Worse, would be if Weygand went over to the ‘Free French’. There were plans in place to occupy the rest of France, but that would involve using forces that might overwise finish off the Soviets. The OKW now had to consider the potential of an invasion of Greece or even Italy itself. Intelligence told them that a new British army was being formed in Iran, and once the British 8th Army had finished with the Italians, these might be available to counter moves towards the Soviet oil supplies.

The onset of the terrible winter weather in Russia had stalled the German advance at the gates of Moscow. What was even more galling was that these ‘impenetrable’ British tanks were appearing there too. The German organization in charge of tank development (Wa. Prüf. 6) was commanded by Oberst Sebastian Fichtner. General Guderian had invited Fichtner to examine the Russian and British tanks captured by his panzer army. Having returned from the Eastern Front with his Special Armour Investigation Committee, he had reported his findings, and General Guderian’s requests.

They identified three advantages the T-34 had over the Panzer III. The first was the sloped armour, which afforded greater protection than flat armour of the same thickness. The second was the suspension; the T-34 used a Christie type suspension which along with its wide tracks gave excellent mobility, even over mud and snow. The third thing was that unlike German tank design which avoided the gun overhanging the front of the tank, the T-34’s longer barrel resulted in better muzzle velocity and thus better armour penetration.

The evaluation of a captured Valiant tank in Russia was relatively dismissive. It was certainly well armoured, but the 40mm gun was obsolescent, the suspension was an old style, without much room for improvement. The diesel engine was considered quite good, but otherwise the tank wasn’t any better than the Panzer III or IV. It was certainly a more impressive tank than the British Matilda Infantry tanks left behind in France, and the ‘cruiser’ style tanks. The new 50mm anti-tank gun was proving effective against the British armour, but only at a closer range than was comfortable for the gunners. The 7.5cm anti-tank gun, expected to begin production in February 1942 would be more than capable, as should the turret mounted version.

As well as these observations, Fichtner included General Guderian’s requests in his report. Firstly, all current tanks should have the minimum of the 5cm gun. New tanks must be made with wider tracks and lower ground pressure to deal with the mud and snow. He emphasised the need for all his panzer to be able to drive cross-country in all weathers. Thinking about the next generation of tanks, he wanted it to have a heavier armament, at least 7.5cm, the armour protection needed improved, the 7.6cm gun on the Soviet tank had to be countered. Finally, the importance of tactical mobility had to be learned. The new tank needed a high power-to-weight ratio, and so a more powerful engine would be essential.

The debate that Fichtner’s report began was between his own preference, to continue with the development of the VK20 project, the design of which was nearly complete. This project had been devised to replace the Panzer III and IV, and adapting it to Guderian’s recommendations would be easier, and faster, than starting from scratch.

On the other hand, the Reich Minister for Armaments and Ammunition, Fritz Todt, wanted to go-ahead and start work on designing a completely new tank. The shock of the T34/KV1, on top of the British Matilda/Valiant success over the panzer arm, asked too many questions of the current thinking. The VK20 project was still limited to 20 to 25 tonnes, what was needed was something that would start at 30 tonnes. The powerplant and suspension of the VK20 project, was in Todt’s opinion, not strong enough to really take the changes that would be needed.

Ultimately the political decision was made to begin work with a design competition between Daimler-Benz and M.A.N. They were requested to develop a tank between 30-35 tonnes, with sloped armour, designed to take Rheinmetall’s 7.5cm cannon, and with an engine providing between 650-700 horsepower, providing a top speed of 55kph. The design was to be ready by the spring of 1942, with prototypes and production models to follow as soon as possible. In the meantime, work on the Panzer III and IV to have additional armour added and the improved cannon fitted would keep these tanks capable of dealing with the enemy.

Progress on the heavier Panzer VI prototypes were being rushed to be ready for the Fuhrer’s birthday in April 1942. This at least would have the armour protection needed to deal with current and projected enemy anti-tank guns, and with the 88mm cannon, it would deal easily with just about anything thrown against it. It was hoped that it would be ready for production in the summer of 1942. Fichtner’s experience of tank development left him worried that such a rush would lead to problems with reliability when it entered service, which the new designation for the 30 tonne tank would likely suffer from too.
threadmark missing @allanpcameron
 

Ramp-Rat

Monthly Donor
Very rarely will I comment about guns and the choices of which gun to place in what bit of kit. However I feel the need to enter the present debate regarding the 17lb/77mm HV, ITTL. So while the British are perusing various fixes to their present problems with regards to the 2lb gun, which was an excellent anti tank weapon, in the early war years, but has rapidly become inadequate in Europe. Note in the Far East, it will remain more than adequate against Japanese armour up until the end of the war. Especially the towed infantry version, which up until the introduction of the recoilless BAT, will remain one of the lightest and easily manoeuvrable infantry anti tank weapons available. However experience in Europe has shown that the 2lb anti tank gun is not man enough for present conditions, and something bigger and more powerful is required. Preferably with a High Explosive round, as tanks spread more time supporting infantry, than they do fighting other tanks. Work on the 6lb replacement, was not stopped by a Dunkirk panic, and so this gun is beginning to be introduced in to service, much earlier than it was IOTL. Work on its replacement is progressing, as the British realise that it the 6lb will soon itself come short of requirements.

The problem with the 17lb gun is it’s weight and size, it’s just a bloody big and heavy gun. Too big for the infantry, who wanted something about the size of the old 2lb gun, and definitely no bigger or heavier than the 6lb gun. Yes the tankers love it, but as they don’t have a tank big enough to carry it, or a turret large enough for a three man crew to serve it and mount it yet. However IOTL, the British did something that they can be brilliant at, they bodged, together from parts they had laying around an excellent gun for their requirements at the time. Yes it wouldn’t have been as suitable for use in the desert, or in the wide open spaces of Eastern Europe. But in the far more restrictive spaces of Western Europe, an effective maximum range of 1000 yards, and an ideal range of 500 yards. What you ended up with, was a gun able to take out any German armoured vehicle, and the majority with a frontal shot. Provided with a more than adequate HE round, which was small and light enough that the Comet could carry 61 rounds, and had they eliminated the hull gunner, could have managed 75 rounds at least. So take part of a 17lb barrel mate it to a modified 20cwt 3in breach, stick a 17lb shell on the front of a 3in cartridge case, and you get the 77mm HV. Will this gun or something very like it be developed ITTL, and much sooner than it was in ours, well I for one believe so, the British just cannot resist a good bodge.

RR.
 
Very rarely will I comment about guns and the choices of which gun to place in what bit of kit. However I feel the need to enter the present debate regarding the 17lb/77mm HV, ITTL. So while the British are perusing various fixes to their present problems with regards to the 2lb gun, which was an excellent anti tank weapon, in the early war years, but has rapidly become inadequate in Europe. Note in the Far East, it will remain more than adequate against Japanese armour up until the end of the war. Especially the towed infantry version, which up until the introduction of the recoilless BAT, will remain one of the lightest and easily manoeuvrable infantry anti tank weapons available. However experience in Europe has shown that the 2lb anti tank gun is not man enough for present conditions, and something bigger and more powerful is required. Preferably with a High Explosive round, as tanks spread more time supporting infantry, than they do fighting other tanks. Work on the 6lb replacement, was not stopped by a Dunkirk panic, and so this gun is beginning to be introduced in to service, much earlier than it was IOTL. Work on its replacement is progressing, as the British realise that it the 6lb will soon itself come short of requirements.

The problem with the 17lb gun is it’s weight and size, it’s just a bloody big and heavy gun. Too big for the infantry, who wanted something about the size of the old 2lb gun, and definitely no bigger or heavier than the 6lb gun. Yes the tankers love it, but as they don’t have a tank big enough to carry it, or a turret large enough for a three man crew to serve it and mount it yet. However IOTL, the British did something that they can be brilliant at, they bodged, together from parts they had laying around an excellent gun for their requirements at the time. Yes it wouldn’t have been as suitable for use in the desert, or in the wide open spaces of Eastern Europe. But in the far more restrictive spaces of Western Europe, an effective maximum range of 1000 yards, and an ideal range of 500 yards. What you ended up with, was a gun able to take out any German armoured vehicle, and the majority with a frontal shot. Provided with a more than adequate HE round, which was small and light enough that the Comet could carry 61 rounds, and had they eliminated the hull gunner, could have managed 75 rounds at least. So take part of a 17lb barrel mate it to a modified 20cwt 3in breach, stick a 17lb shell on the front of a 3in cartridge case, and you get the 77mm HV. Will this gun or something very like it be developed ITTL, and much sooner than it was in ours, well I for one believe so, the British just cannot resist a good bodge.

RR.
Seems plausible. Hells, they might just end up with the OTL 77mm.
 
Seems plausible. Hells, they might just end up with the OTL 77mm.
Which would be a Good Thing.

Can we simply presume that the eventual late war tank gun (Victor 2 or successor - Vulcan? Vigilante?) is of either 75mm or 76.2mm calibre. And has the same hole punching and HE performance as tge OTL "77mm".

And then let our esteemed author worry about the details of which calibre and what arguments Vickers and the authorities engaged in to get that result.
 
Which would be a Good Thing.

Can we simply presume that the eventual late war tank gun (Victor 2 or successor - Vulcan? Vigilante?) is of either 75mm or 76.2mm calibre. And has the same hole punching and HE performance as tge OTL "77mm".

And then let our esteemed author worry about the details of which calibre and what arguments Vickers and the authorities engaged in to get that result.
I can agree with that.

In other stuff, Force Z is looking to be a major force, with two battleships an battlecruiser, a carrier, and numerous cruisers and destroyers, as opposed to the OTL one battleship, one battlecruiser and a handful of destroyers.
 

Ramontxo

Donor
What I mean was, I'm not seeing a ling between failed Italian HEAT and the British developing HESH.


I figured as much.


Fair.
Sorry it is obvious there have been an misunderstanding. I never pretend the British work on Hesh rounds come from the E. P. Italian shells. And for whatever it is worth AIAI the Polish used soft metal shells in their high velocity AT rifles to get an similar effect.
 
28 November 1941. Nottinghamshire, England.
28 November 1941. Nottinghamshire, England.

Welbeck Abbey had become home to the 43rd Bn RTR, or “43rd (6th City) Battalion, The Royal Northumberland Fusiliers, Royal Tank Regiment” to give them their full title. As with a number of pre-war territorial units, it had been converted to an armoured role. Along with two other such battalions, 144th and 148th Royal Armoured Corps (formerly 9th Loyal Regiment North Lancashire and 8th East Lancashire Regiment) made up 33rd Army Tank Brigade.

43rd Bn RTR had been chosen for this particular role because it had been lucky enough to have some Matilda II and Dragon artillery tractors to train on after Dunkirk. Having done so, they would now pass on this experience to the two new RAC regiments. Those Matilda II tanks had been passed on to other units, and now 43rd Bn RTR were the first unit to be equipped with the new A22 Infantry Tank Mark IV. Known as the ‘Churchill’, this Vauxhall product had been through a lot of development before being issued to a tank battalion, but it was still a rush job.

Some of the officers and men of the Battalion had been detached to Vauxhall and to some of the other firms making the tanks, especially Broom & Wade, Beyer Peacock and Gloucester Railway. Others had gone to the factories to learn about the Bedford twin-six engine, and others to learn about the new gear box, steering gear and final drive.

Having worked alongside the civilian workers to learn about their new tanks, some of these same civilians were now at Welbeck Abbey working with the soldiers to master the complexity of a new type of tank. Brigadier Roy Jerram, OC 33rd Army Tank Brigade, had very particular orders. The numbers of A22s being delivered on a monthly basis would equip his Brigade by early next year. Each of the three battalions had been issued twenty tanks initially, for familiarisation. Once the men and machines were ready, then Jerram would have to work out the best use of this new Infantry Tank.

Differing from previous Infantry Tanks, the Churchill resembled the French Char B1 (bis) in that the turret contained the standard 2-pdr gun, and also had the 3-inch tank howitzer mounted in the hull. Normally only Close Support tanks were armed with the howitzer, but this was on all the tanks. The difficulty for the hull gunner to make best use of the howitzer had led to a request for a new prototype from Vauxhall for a Mark II, which would replace the howitzer in the hull with a Besa machine gun, and have the usual mix of gun and CS tanks using the 2-pdr or 3-inch howitzer.

The reviews of the battles in Libya had called for a greater use of HE shells, and there was a case to be made of replacing the 2-pdr in the turret with the 3-inch howitzer, and having these as the majority of tanks in the battalion, with one 2-pdr tank in each troop. Jerram’s findings would be play a big part in the decision about the best way forward. Already the concept of the Infantry Tank protecting the infantry from enemy tanks, therefore needing the penetration of the 2-pdr, had been refuted in combat experience. An Infantry Tank supporting the infantry had to be capable of overcoming prepared enemy defences, for which an HE shell was much more useful.

Once more the threat of invasion was remote, between the winter weather and the German commitment in Russia, meant that the army could focus over the next few months on training. As Brigadier Jerram sat with his senior officers working out a full training program for the next few months, it was difficult not to be sceptical about the new tanks. As a replacement for the Matilda Infantry Tank II it wasn’t much of an improvement, except in armour protection, now four inches thick at the front. The men weren’t too impressed with the problem of trying to fight a vehicle with two main guns, especially as the howitzer had such a limited traverse and elevation. Because the 3-inch howitzer had been designed to be fitted into the 2-pdr mounting, the armourers were fiddling about, trying the idea of the howitzer in the turret, allowing for more ammunition storage for the HE and smoke shells.

The mobility of the new tank was impressive over obstacles, the Merritt-Brown transmission allowed the drivers to take the tank places that most tanks would avoid. The power to weight ratio wasn’t great, and it was extremely noisy, reminding some of the oldest men of the early tanks of 1916. Brigadier Jerram had commanded a Mark IV tank at Cambrai, and had commanded a Squadron of Matilda I and IIs of 7th Bn RTR at Arras in 1940, later becoming its CO. Thinking back to that fight, going up against the Czech made tanks of 7th Panzer Division, he couldn’t help feel that the new Churchill tank had learned more from the lessons of the fighting in Flanders and France in 1917 or 1918 than from 1940. The Churchill would have been an unbeatable tank over the trenches and shell holes. For what lay ahead in 1942 and beyond, he just wasn’t convinced that this was the machine that would win a war.
 
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Well the mountain-goat has been a while in coming, but it’s finally here. Now just to find a use for it. Engineering would seem to be the best IMO.
 
Just curious as it's rarely mentioned, but why were the 3.7" howitzers (adapted mountain gun?) used in the Cruiser MkII's discarded and replaced with the 3" howitzer? I often wondered if it had to do with some backroom deal.where the Royal Artillery finally allowed Armoured to carry HE (instead of mostly Smoke) on the condition they didn't exceed 3".

Anyone know for certain how that all came to pass?
 
Just curious as it's rarely mentioned, but why were the 3.7" howitzers (adapted mountain gun?) used in the Cruiser MkII's discarded and replaced with the 3" howitzer? I often wondered if it had to do with some backroom deal.where the Royal Artillery finally allowed Armoured to carry HE (instead of mostly Smoke) on the condition they didn't exceed 3".

Anyone know for certain how that all came to pass?
From what I've read, and mentioned in the last update, was that the 3-inch howitzer was designed to fit into the 2-pdr mounting. I imagine that is why it was mediocre at best.
Allan
 
Just curious as it's rarely mentioned, but why were the 3.7" howitzers (adapted mountain gun?) used in the Cruiser MkII's discarded and replaced with the 3" howitzer? I often wondered if it had to do with some backroom deal.where the Royal Artillery finally allowed Armoured to carry HE (instead of mostly Smoke) on the condition they didn't exceed 3".

Anyone know for certain how that all came to pass?
The 3.7 inch gun was a beast in terms of weight.

Lets put it this way. Wiki gives the weight of the 3 inch howitzer as 103 kg. The interrupted screw breach of the 3.7 inch howitzer was 112kg.

Now I can't find a decent source for the weight of the 3.7 inch gun on a tank. Wiki quotes 730 kilos but that might be for the full rig including carriage as a howitzer rather than just the gun. It might not be.
 
Just curious as it's rarely mentioned, but why were the 3.7" howitzers (adapted mountain gun?) used in the Cruiser MkII's discarded and replaced with the 3" howitzer? I often wondered if it had to do with some backroom deal.where the Royal Artillery finally allowed Armoured to carry HE (instead of mostly Smoke) on the condition they didn't exceed 3".

Anyone know for certain how that all came to pass?
I think the 3" gun and breech were lighter (total of 116 kilos) and actually designed for AFV work, while the 3.7" was a larger weapon that had been designed before WW1 and not for AFVs - its Breech alone was 112 Kilos.

So I suspect it was a combination of old design, weight, size and the size of the ammo (more 3" could be carried?)

While the 3.7" had a longer range the 3"s range would have been sufficient for then tank work.

Also I have often seen the claim that tanks did not carry HE because the Royal Artillery would have a hissy fit!

But I do not recall ever reading any evidence that this was the case and I suspect it was because the 2 pounder was simply too small to carry an effective HE round (HE rounds for the gun would contain the same explosive charge of a hand grenade) so they initially did not bother and the 'CS' tanks where intended to fire 'Chemical / Smoke' rounds with the need for HE only becoming apparent in 1941 in the desert.

I think it was most likely a doctrinal thing.
 
And now, I'm wondering if a Soviet 76.2mm gun 'accidentially' makes its way back to Blighty, and into the hands of these enterprising types.
 
And now, I'm wondering if a Soviet 76.2mm gun 'accidentially' makes its way back to Blighty, and into the hands of these enterprising types.
The F-34 was a distant descendant of the Russian Model 1902 field gun, similar to how the 75 mm M3 was a distant descendant of the French Model 1897 field gun.

US M72 AP out of a 75 mm L/40 M3 gun (6.32 kg @ 619 m/s) on a Sherman carried 1.2 MJ of muzzle energy. The Russian F-34 fired AP (6.3 kg @ 680 m/s) that carried 1.45 MJ of muzzle energy. For comparison, the US 76 mm Gun M1 fired M62A1 APCBC (7 kg @ 792 m/s) with 2.2 MJ of muzzle energy and the UK 77 mm HV fired APCBC (7.7 kg @ 785 m/s) with almost 2.4 MJ of muzzle energy.

The Russian gun has very little advantage over the existing option on the Sherman and is inferior to any sort of 3-inch class HV gun that the British have in development. For comparison, the 6-pdr APCBC projectile (3.23 kg @ 831 m/s) carries 1.1 MJ of muzzle energy. The reason the 6-pdr could serve as the basis for the QF 75 mm was because they were already quite similar in size.
 

marathag

Banned
Difficult, since such a gun is by no means small, and the Soviets are pretty watchful of foreigners.
US got a T-34 and KV-1 for Testing in late 1942
The reason the 6-pdr could serve as the basis for the QF 75 mm was because they were already quite similar in size.
Size of cartridge, and for overall power

QF 6 pdr 57mmx441mm with 90mm rim diameter was about 2.6 lbs Propellant mass. Gun tube weight 761 pounds
75mmX350mm with rim diameter of 87mm and less than 2 lbs Propellant mass. tube weight 893 pounds
I think the 3" gun and breech were lighter (total of 116 kilos) and actually designed for AFV work, while the 3.7" was a larger weapon that had been designed before WW1 and not for AFVs - its Breech alone was 112 Kilos.

So I suspect it was a combination of old design, weight, size and the size of the ammo (more 3" could be carried?)

While the 3.7" had a longer range the 3"s range would have been sufficient for then tank work.
3.7" had 92mm long cartridge, and 111mm rim. This was separate loading, not 'fixed' ammunition 290m/s velocity for the A9 and A10 tanks
The Breech block sounds overbuilt for that role, the US M2 75mm howitzer that had a 272mm long cartridge with 87mm rim, the tube and breech weighed 318 pounds total for the M2, and operated at far higher pressure and almost a third more range of the 3.7"

The US 105mm with a 372mm case and 119mm rim, that tube and breech weight was 955 pounds, making it fairly interchangeable with the M3 75mm
 
I think the 3" gun and breech were lighter (total of 116 kilos) and actually designed for AFV work, while the 3.7" was a larger weapon that had been designed before WW1 and not for AFVs - its Breech alone was 112 Kilos.

So I suspect it was a combination of old design, weight, size and the size of the ammo (more 3" could be carried?)

While the 3.7" had a longer range the 3"s range would have been sufficient for then tank work.

Also I have often seen the claim that tanks did not carry HE because the Royal Artillery would have a hissy fit!

But I do not recall ever reading any evidence that this was the case and I suspect it was because the 2 pounder was simply too small to carry an effective HE round (HE rounds for the gun would contain the same explosive charge of a hand grenade) so they initially did not bother and the 'CS' tanks where intended to fire 'Chemical / Smoke' rounds with the need for HE only becoming apparent in 1941 in the desert.

I think it was most likely a doctrinal thing.
2 Pdr did have a HE round and I am fed up with ignorant comments about it. The 2 Pdr round was a nose fused round designed to destroy material and AT guns. The Australian 2 Pdr round was a base fused round and designed to destroy bunkers and strongpoints. The British round was initially reserved for RA crews of AT guns. When the AT guns were given to the infantry, they were provided with HE rounds and trained on how to use them. Armoured crews were felt too "amateaurish" compared to AT gun crews and were initially denied them. They however felt they didn't need them, being concerned with the destruction of tanks. Once they appreciated the value of HE rounds, the 2 Pdr had been given primarly over armoured cars. Armoured cars by this stage were armed with 75mm guns but those regiments that were equipped with 2 Pdrs were faced with a choice - either they used Little John adapters or they stuck with standard 2 Pdrs able to fire HE. What happened in the end was all bar one or two of each troop stuck with the Little Johns and the rest stuck with standard 2 Pdrs able to fire HE. Downunder they still used Matildas and they stuck with standard 2 Pdrs, able to fire HE.
 
I think the 3" gun and breech were lighter (total of 116 kilos) and actually designed for AFV work, while the 3.7" was a larger weapon that had been designed before WW1 and not for AFVs - its Breech alone was 112 Kilos.

So I suspect it was a combination of old design, weight, size and the size of the ammo (more 3" could be carried?)

While the 3.7" had a longer range the 3"s range would have been sufficient for then tank work.

Also I have often seen the claim that tanks did not carry HE because the Royal Artillery would have a hissy fit!

But I do not recall ever reading any evidence that this was the case and I suspect it was because the 2 pounder was simply too small to carry an effective HE round (HE rounds for the gun would contain the same explosive charge of a hand grenade) so they initially did not bother and the 'CS' tanks where intended to fire 'Chemical / Smoke' rounds with the need for HE only becoming apparent in 1941 in the desert.

I think it was most likely a doctrinal thing.
Unfortunately they frequently did not have smoke rounds either.
 
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