Tank & AFV armament alternatives, 1935-45 (5 Viewers)

[tomo pauk]

<snip>

I'm telling you again: the book about the French tanks and guns developments between 1933 and 1940 is long overdue

 

[Shortround6]

I'd guess that two H35s will cost at least as much as one S35, while needing double the number of trained crew
440 of S35 produced before mid 1940 is still very good. Too bad that French didn't doubled-up on the S35, foregoing the H35 all together, for yet another 600+- of the S35s instead of 1200+- of H35s.
French tank production, in numbers and let alone in tonnage was better than what Germans were doing, pointing out that they in fact that they have had the plants/factories to make stuff. Unfortunately, best of the production capacity was used up for making the under 12 ton tanks crewed by two men each.

The little tanks only need 50% more crew

France didn't have had the time because they were defeated by Germany. As it can be seen, production of the serious tanks in Germany was also not roses and unicorns.
If the S35 can have a 2-men turret in the operative tanks in summer of 1940, that is a major boon for them. Having that in, say, October is indeed too late for 1940.

You are right, the German production was not roses and unicorns but it was several months ahead of where the French needed to be. It takes quite a number of months to go from first tank out the factory door to having significant numbers in service in the field. Germans are going to get 5cm guns in MK IIIs sooner than the French are going to get improved tanks ( 2 man turrets, etc)

The 75mm gun on the Char B was a good start. An excellent start when compared to what the other people were installing in their tanks in the second half of the 1930s

The 75mm gun on the Char B was not really a good gun, however it's location well and truly sucked. The whole system was ingenious, However they were answering questions that should not have been asked, or at least not repeated more than once in the meetings. Just because you can design a steering system that allows you to use a fixed gun and use the driver as a gunner doesn't mean you should. At least the US was only dumb enough to try to the use the driver to aim/fire axillary machine guns and not the tanks main armament, it's reason for being. Coordination between the commander (if he wasn't playing with the 47mm gun) and the driver to aim and fire the 75mm gun needed to be of a high order. This assumes that the commander can see targets the gunner cannot. Commander has to guide the driver to line up the tank with the target, at least until the gunner can see the target in his view port or sight. Somebody had to the tell the loader which type of ammo to stick in the gun. Driver has to steer the tank for any correction left and right and may or may not have to take is right had off the controls to operate the gun elevation wheel. A few commanders and drivers seemed to get this to work well but this may have been a minority.
Grants and Stugs, Su-85s and such had limited traverse of the gun by the gunner. You had a proper commander, gunner, driver, loader division of duties.

I would note that tank turret design is not quite as simple as it seems. French may have been able to muck this one up at times. Chieftain claims that the French FCM 36 could not be upgraded to the 37mm SA 38 gun because the increase recoil broke some of the welded seams in the turret. A new turret was under test when France fell? The recoil of a 700g projectile at 700ms being too much for the turret?
A two man turret is better than a one man turret. How close does it get you to the three man turret? And it is not just the increase in the rate of fire. It is that the 3rd man (1st man?) is maintaining situational awareness (where the tank is, where his platoon mates are, where the enemy is, is the enemy moving, what is the priority list of the visible enemy targets, as an enemy disappeared from visibility/sneaking up).

 

[tomo pauk]

The little tanks only need 50% more crew

They will need 100% more of the drivers and commanders/gunners/loaders, though.

You are right, the German production was not roses and unicorns but it was several months ahead of where the French needed to be. It takes quite a number of months to go from first tank out the factory door to having significant numbers in service in the field. Germans are going to get 5cm guns in MK IIIs sooner than the French are going to get improved tanks ( 2 man turrets, etc)

What are the monthly production figures for 1940? For the tanks above 15 tons?
The 5cm gun on some Pz-IIIs still does not solve the problem of that tank being a fair game for the 25mm ATG and better.

The 75mm gun on the Char B was not really a good gun, however it's location well and truly sucked.

I'd agree with the second half of the sentence, but not with the 1st half.

 

[Elan Vital]

What are the monthly production figures for 1940? For the tanks above 15 tons?

The subject of German production plans and capability for a prolonged war with France deserves its own book IMO. The main difficulty is knowning what technological/industrial delays were incompressible (factories starting construction before 1940, but that cannot be completed any earlier) and which ones weren't (factories and tech ordered only sometime after Barbarossa when the war took on a new shape).

For Pz IV (chart at the very bottom): sustained 30/month. Pz III was IIRC around 80/100/month intended. It is a July 1940 document, but I'm not sure the Germans could really ramp up production much for the remainder of 1940 anyway. 1941 wasn't a huge change OTL, but OTL 1942 might give some indications with the caveat that this could include some of these newly added capacities with incompressible delays.

Last I recall, France alone matched German production of tanks above 15 tonnes and would be more or less able to follow, but the UK alone could add as much as 200/month by 1941 split roughly 50/50 Infantry/Cruisers.

 

[Shortround6]

What are the monthly production figures for 1940? For the tanks above 15 tons?

For the French
Production de chars et automitrailleuses, 1939-1940
It seems like 66-70 tanks above 15 tons was planned production for most of 1940.
Germans built about 1400 Pz III & Pz IV in 1940 total and about 367 Pz 38(t)s which while not 15 ton tanks were a lot better than the French two man tanks.

The 5cm gun on some Pz-IIIs still does not solve the problem of that tank being a fair game for the 25mm ATG and better.

Germans were fitting the extra 30mm plates to the MK IIIs starting in Aug 1940. This is somewhat independent of the 50mm guns, I don't think any 37mm armed tanks got the extra plates but if the BoF was still going on there doesn't seem to be any technical reason they couldn't be fitted.

I'd agree with the second half of the sentence, but not with the 1st half.

I am not sure what you get for the weight and complications aside from more HE.

 

[tomo pauk]

Germans built about 1400 Pz III & Pz IV in 1940 total

Do you have some link about that? There seems to be only 290 of Pz-IV made in all of 1940.

Germans were fitting the extra 30mm plates to the MK IIIs starting in Aug 1940. This is somewhat independent of the 50mm guns, I don't think any 37mm armed tanks got the extra plates but if the BoF was still going on there doesn't seem to be any technical reason they couldn't be fitted.

Okay.

I am not sure what you get for the weight and complications aside from more HE.

One 75mm HE shell was worth perhaps as much as five 47mm HE shells? All while not being a wimp when it is enemy tanks.
We can see that the target effect of the 75mm shell was acknowledged by the British in Summer of 1940.

 

[Shortround6]

Getting back to the British and some the reasons they did what they did.
And a lot of it had to do with money.
When they went from the A 13s to the Covenanter and Crusader they were trying to to do several things. One was change the transmission/steering gear and the 2nd was to shift of 40mm frontal armor instead of 30mm.
For some reason they decided that the tank/s had to weigh under 18 tons to suit the existing bridging equipment. And the solution to this was to shorten the tank in height so that it would need less armor. It was this shorter height that created the problems of Meadows flat 12 and need to chop about 7in out of the Liberty engine and use the squashed turret.
This is a classic own goal or shooting themselves in the foot, not once, but several times.
The Royal Engineers were already working on and nearly done with bridging equipment to suit the A 12 Infantry tank (Matilda) that was called class 24 tons (British long tons).
The Bridge thing was the official excuse. Perhaps it just gave cover to those who wanted lightweight (cheap) for other reasons.
This was a real opportunity for the British to make a decent cruiser (medium ) tank with more growth potential.

Crusader prototype. Note not only the little mg turret on the bow but that the driver has his own Besa gun mounted to the right of his head.
He can't see to the left around the little turret and he has trouble seeing out the right around the Besa guns breech. He can open the hatch and look out the front to drive but is in serious of danger of head injury if the main gun turns/depresses.
One can see why they got rid of it.
But why was it there to begin with????
The A13s had one gun in the tank, the Crusader started with 3, went to 2 very quickly and after early combat, would up with one. But it had to deal with size/space/weight for it's entire life. BTW the early testing with the little machine gun turret did not go well. The gunner lost consciousness after firing 400 rounds. It proved impossible to pull him out of the turret/firing position. After opening up all hatches and suppling air/oxygen(?) it took 45 minutes for him to wake up. Just needed a little tweaking of the ventilation, right?
While the Liberty powered A 13s were hardly trouble free the modifications done to it to get to fit into the lower hull really screwed things up. Changes to the cooling fans and fan drives (ring any bells) and the change to oil system (shallower oil pan/sump) required 7 fittings and exterior oil line/s instead of a single connection. Also screwed up the oil scavenging in the engine when not operating on the level.

This is what "it if".
What if the British tried to make a super A 13 with the same armament, more armor, room for growth (instead of cramming in machineguns for everybody) and used the higher weigh limit of the Matilda tank bridge.?

 

[tomo pauk]

What if the British tried to make a super A 13 with the same armament, more armor, room for growth (instead of cramming in machineguns for everybody) and used the higher weigh limit of the Matilda tank bridge.?

They would've been getting something like 80% of a Cromwell?

 

[Shortround6]

Maybe.
Go for 50mm frontal armor to start, not 40mm. They would up increasing it anyway. Add a little more to the sides.
Taller hull and bigger turret might allow room for 6pdr in 1941 or 6 months-year earlier? and still keep 3 man turret crew. Improve cupola, not get rid of it.
Buy time to sort out the next phase. Meteor powered Cromwell/Comet with the 77mm gun, may even a sloped glacis plate if we can keep the bow gun from coming back
British Panther Junior in 1943?

 

[Elan Vital]

This is what "it if".
What if the British tried to make a super A 13 with the same armament, more armor, room for growth (instead of cramming in machineguns for everybody) and used the higher weigh limit of the Matilda tank bridge.?

They would've been getting something like 80% of a Cromwell?

Maybe.
Go for 50mm frontal armor to start, not 40mm. They would up increasing it anyway. Add a little more to the sides.
Taller hull and bigger turret might allow room for 6pdr in 1941 or 6 months-year earlier? and still keep 3 man turret crew. Improve cupola, not get rid of it.
Buy time to sort out the next phase. Meteor powered Cromwell/Comet with the 77mm gun, may even a sloped glacis plate if we can keep the bow gun from coming back
British Panther Junior in 1943?

This is pretty much the what-if conclusion from P.M. Knight's book on Crusader. Bonus point is that the reasoning behind the Covenanter/Crusader separation (mounting an auxiliary turret while staying under 18 tons) would no longer exist, so you would reduce the number of tank variants. Would also make Meadows' solution of a flat 12 built out of truck engine blocks impractical, so could force proper development of a dedicated tank engine within the space of the Liberty, but more powerful.

In an even more ideal world, this idea would have been realized as early as the A16, replacing 3 programs (A16, A13 Mk III and A15) with a single one started a little earlier than IRL A15. Now all that remains is turning the Vulcan/LMS/ROF A14 program into the proper spiritual replacement for Matilda II and nipping the A20 and A22 concepts in the bud* and the British are set.

*Shelled Area tanks IMO only make sense if they are designed like the TOG 2 from the start as a counterpart to the French fortification assault tanks.

 

[tomo pauk]

Germans built about 1400 Pz III & Pz IV in 1940 total and about 367 Pz 38(t)s which while not 15 ton tanks were a lot better than the French two man tanks.

FWIW, Germans lost in the West, during May and June of 1940, 135 of Pz-IIIs, and 97 of Pz-IVs. That is per Jentz' 'Panzertruppen', part 1; numbers are for a total loss tanks. He also notes the report made in the 3rd Panzerbrigade that the Pz-IV was the best tool for outright defeating the Entente tanks; often the Pz-III needed to close the distance so the 37mm gun can do it's job against the enemy tanks. The AP shots from the 37mm often bounced from the French tanks armor. Brigade report also notes the high effectiveness of the 75mm shells against the AT emplacements. The best Entente AT gun rated by that report is the 2pdr (can pierce the best German stuff at 800 m), with the French tank gun of 47mm does it at under 600 m, and so is the 47mm AT gun.

(as noted above, the total production of the Pz-IVs in 1940 was 290 tanks)

 

[Shortround6]

Well, the Pz III with the 37mm was under armed for it's weight. Way under armed.
the 37mm gun in the Pz 38(t) was almost 15% more powerful than the 37mm gun in the Pz III.
The 37mm gun the Pz 38(t) was about 33% more powerful than the French long 37mm gun (37 SA 38) in the French 2 man tanks.
Not saying that the Pz 38(t) was Somua killer but some people were not getting a good return on their tank tonnage.
I would also note that the Germans upgraded the 38 (t) to 50mm of armor starting in the fall of 1940. Only on the front. At first by adding a 2nd 25mm plate to certain areas and much later the they used a one piece 50mm plate. The 38 (t) had the problems of a two man turret.

If the French don't surrender and the war drags on a lot depends on what French factories remain French, What the supply of AT guns to the French are in addition to the tanks.
It did take the Germans from March of 1940 to Feb 1941 to build 200-202 of the Panzerjäger I. Only about 5 platoons in the BoF ?
The Pac 38 was entering production during 1940. Possibly showing up in late fall or early winter?

 

[tomo pauk]

Well, the Pz III with the 37mm was under armed for it's weight. Way under armed.
the 37mm gun in the Pz 38(t) was almost 15% more powerful than the 37mm gun in the Pz III.
The 37mm gun the Pz 38(t) was about 33% more powerful than the French long 37mm gun (37 SA 38) in the French 2 man tanks.
Not saying that the Pz 38(t) was Somua killer but some people were not getting a good return on their tank tonnage.

I would also note that the Germans upgraded the 38 (t) to 50mm of armor starting in the fall of 1940. Only on the front. At first by adding a 2nd 25mm plate to certain areas and much later the they used a one piece 50mm plate. The 38 (t) had the problems of a two man turret.

Agreed.

If the French don't surrender and the war drags on a lot depends on what French factories remain French, What the supply of AT guns to the French are in addition to the tanks.

The 47mm ATG is there to stay. Perhaps the tripod carriage is introduced (granted, that does not improve the penetration), and certainly the better ammo for it and for the 47mm tank gun. Light tanks might be getting the equivalent of the high-velocity (850 m/s with 'normal' ammo) 37mm fortress gun, both with and without the APCR ammo.
The 75mm gun gets the AP ammo and suitable sights.

I will not speculate about the squeeze bore stuff that French were also mooting.

It did take the Germans from March of 1940 to Feb 1941 to build 200-202 of the Panzerjäger I. Only about 5 platoons in the BoF ?
The Pac 38 was entering production during 1940. Possibly showing up in late fall or early winter?

Germans slept on the Czech 47mm gun. Having it in a self-propelled mount (either the PzJgd-1 or on the Pz-III) by hundreds would've mean the more smooth sailing in 1940.
We'd certainly see the 5cm and 47mm by hundreds in German hands if the war had dragged on into 1941 in the West, as well as the up-armored tanks/AFVs of all combatants. Germans would've felt compelled to do something about the Matilda II tanks, too...

 

[Shortround6]

The 47mm ATG is there to stay. Perhaps the tripod carriage is introduced (granted, that does not improve the penetration), and certainly the better ammo for it and for the 47mm tank gun. Light tanks might be getting the equivalent of the high-velocity (850 m/s with 'normal' ammo) 37mm fortress gun, both with and without the APCR ammo.
The 75mm gun gets the AP ammo and suitable sights.

I am not sure that the French APCR ammo will work (do what you want) in the high velocity guns. Or be worth the cost? The Fortress 37 already has APCBC ammo. You could design an APCR round using a tool steel core like the 37mm SA 18 gun but I am not sure that tool steel will hold up at the higher velocities. You may need actual tungsten carbide for that.
French need an entire new light tank.

But the French seemed to take forever to go from planning/ prototype to actual production. Trying to up armor and drop in a new engine might have resulted in next to nothing in 1940/41. At least it had a two man turret

I will not speculate about the squeeze bore stuff that French were also mooting.

I won't either, except to say that I don't know how long the Germans were working on their squeeze bore stuff before they came out with it in 1941. What level of resources they put into the 3 projects. It was also sort of a dead end.

Germans slept on the Czech 47mm gun. Having it in a self-propelled mount (either the PzJgd-1 or on the Pz-III) by hundreds would've mean the more smooth sailing in 1940.
We'd certainly see the 5cm and 47mm by hundreds in German hands if the war had dragged on into 1941 in the West, as well as the up-armored tanks/AFVs of all combatants. Germans would've felt compelled to do something about the Matilda II tanks, too...

Too much NIH ?
Sticking the Czech 47 in a Pz-II chassis might have been interesting
Germans had something for the Matilde II. It might require getting to around 200-300 meters. The APCR shot, but they don't have much. The more they shoot up in France the less they have for Russia.

 

[tomo pauk]

I am not sure that the French APCR ammo will work (do what you want) in the high velocity guns. Or be worth the cost? The Fortress 37 already has APCBC ammo. You could design an APCR round using a tool steel core like the 37mm SA 18 gun but I am not sure that tool steel will hold up at the higher velocities. You may need actual tungsten carbide for that.

French surviving in a decent shape for 1941 have all of 1940 to figure out what kind of APCR works, and in what guns. Their access to tungsten will be less troublesome than the German access to it.
The APCBC ammo for the fortress gun (900g shot at 850 m/s) should came very close to the the US 37mm with the APC(BC) ammo (870 g at 870-884 m/s), ie. able to defeat 50mm of the up-armored front of Pz-III at 500-600 yds (and up to 2000 yds for the side shots).

Too much NIH ?
Sticking the Czech 47 in a Pz-II chassis might have been interesting
Germans had something for the Matilde II. It might require getting to around 200-300 meters. The APCR shot, but they don't have much. The more they shoot up in France the less they have for Russia.

German taking advantage of the captured stuff, except just to use what is found in the warehouses, was pretty bad, or it was late.
Czech 47 on the Pz-II should give them a vehicle with less compromises than the lash-up the PzJgd-I was. German 75mm field pieces would've also worked great on the Pz-II chassis, sorta Marder minus. Give them an APCR and it is at least as good as the F34 with it, or the US 75mm HVAP. Will work against the Matilda II beyond 500m.

Ideally for them, Germans would've been best served with an up-armored Pz-IV that is armed with the spin-off from the 75 field guns. Gives them a Sherman equivalent, and very early (1939 with hindsight, 1941 without the hindsight but with lessons learned in France incorporated), and it is still much more useful than any of the tanks armed with the short 75mm that the Germans fielded as late as in summer of 1943.

I won't either, except to say that I don't know how long the Germans were working on their squeeze bore stuff before they came out with it in 1941. What level of resources they put into the 3 projects. It was also sort of a dead end.

Squeeze bore guns make no sense without the cored shot, an core better be from tungsten carbide.
One such gun, talk 75/55 as it was mooted, + it's ammo supply would've probably cost as much as mounting three existing 75mm pieces on a split carriage + the addition of a cored shot into an inventory. And French have thousands of 75mm guns, that still can do a good work as field guns.

 

[Elan Vital]

Light tanks might be getting the equivalent of the high-velocity (850 m/s with 'normal' ammo) 37mm fortress gun, both with and without the APCR ammo.


I will not speculate about the squeeze bore stuff that French were also mooting.

The French concluded that squeezebore was not very worth it at tank gun level (or even high calibers) and focused on it to develop lightweight high penetration guns for the lowest levels of the infantry where a normal (even light) AT gun would be inconvenient.

While it is plainly obvious that the 37mm fortress gun requires a smaller volume and lower weight to operate than the long 47 (100mm shorter case already, and smaller and lighter gun on the level of the 2pdr or 37mm M6), the future light tanks were meant to move on the 47mm tank gun so I'm not sure the French would have wanted to go backwards in terms of HE payload even to obtain increased penetration. Moreover, even that 37mm will most likely reach the threshold where the French mandate a 2-man turret (starting from a certain cartridge size/weight, a dedicated loader was mandated), which will by itself require a quantum increase in vehicle size/weight.
I suspect that the French wouldn't have bothered with such an intermediate and short/lasting solution and would have accepted moving straight to a 2-man long 47 turret light infantry tank, if that class is to remain. Both solutions would have required severe changes in technology (engine*) and/or logistical class to cope. This would mostly be a matter of figuring out if an intermediate logistical weight class between 20 and 35 tonnes (the existing thresholds) could be devised.

*while the 1-man turret future light tanks were presently mooted with 200-230 hp class straight-six engines with potential for more power if fully developped, such upscaled tanks might instead benefit from the lower end of the battle tank engines in development in 1939 with 340 hp, as the battle tank class had itself moved to beyond 400 hp with slightly enlarged derivatives of these engines in 1940.

French need an entire new light tank.
View attachment 809919
But the French seemed to take forever to go from planning/ prototype to actual production. Trying to up armor and drop in a new engine might have resulted in next to nothing in 1940/41. At least it had a two man turret

I won't either, except to say that I don't know how long the Germans were working on their squeeze bore stuff before they came out with it in 1941. What level of resources they put into the 3 projects. It was also sort of a dead end.

Too much NIH ?
Sticking the Czech 47 in a Pz-II chassis might have been interesting
Germans had something for the Matilde II. It might require getting to around 200-300 meters. The APCR shot, but they don't have much. The more they shoot up in France the less they have for Russia.

The development timeframes can be a little skewed by the fact most French tank types in service in 1940 were introduced in 1935/36 while we will never know for sure when the successors would have actually been fielded. But other than particular cases, it wasn't really much slower than other countries.

The light tanks were mooted in 1933, deliveries start in about 1936.
SOMUA mooted in 1933, deliveries start in 1937 or so.
B1 is exceptionnal as you could almost consider it as multiple tank programs back to back, the tank itself changed quite radically between 1921 and 1935
D2 mooted in 1930, deliveries in 1936 or so.

In comparison, Z.W started at least as early as 1933/34 and took until 1938 for early production types to come out?

It seems to me that unless the specifications change completely, development to production takes on average 3-5 years for an interwar tank.

In the case of Renault, while the accusations of conservatism and excessive cost-cutting (at the expense of part durability) are quite valid for all their tanks up to 1935, it also seems extremely apparent to me that they bit off more than they could chew at the time. In several critical years, Renault had to work simultaneously on:
- AMR 33/35 recon vehicle
- Renault R35
- their parts of B1
- AMC 35
- D1 and D2

I am afraid that even if the French Army had provided funding for a lot of each of these items at once, Renault would have been unable to actually get things done in a sane manner.

I still personally think it would have been highly valuable if APX or ARL continued working on the APX-2 2-man turret to modernize it, even if at the minimum it was just uparmoring it, deleting rivets/bolts and replacing the diascopes with PPL 160 episcopes. It was a real missing link between the 1-man turrets and the large 2/3-man turrets for long 47 or 75mm.

 

[Shortround6]

The French concluded that squeezebore was not very worth it at tank gun level (or even high calibers) and focused on it to develop lightweight high penetration guns for the lowest levels of the infantry where a normal (even light) AT gun would be inconvenient.

Agree. The squeeze bore may be attractive for a towed (man, horse or light truck) AT gun where there are other nearby weapons to deal with a variety of enemy targets, it tends to loose it's appeal for tank use. The German 42/28mm (actual diameter differed) fired an HE shell with a whopping 25grams of HE. Not a good return on investment/s made. The Taper bore guns also tended to use up barrels rather quickly. British were worried about shooting out 6pdr AT gun barrels with HE. The taper bore gun barrels were going to give up in a fraction of the number of shots. Armor penetration much better than the 37mm even with APCR but the 37mm offers about 50% more HE (depending on shell) and much, much better barrel life. In part because it used much less propellent per shot. The taper bore guns are too specialized for general tank work as apposed to specialized tank destroyers.

While it is plainly obvious that the 37mm fortress gun requires a smaller volume and lower weight to operate than the long 47 (100mm shorter case already, and smaller and lighter gun on the level of the 2pdr or 37mm M6), the future light tanks were meant to move on the 47mm tank gun so I'm not sure the French would have wanted to go backwards in terms of HE payload even to obtain increased penetration. Moreover, even that 37mm will most likely reach the threshold where the French mandate a 2-man turret (starting from a certain cartridge size/weight, a dedicated loader was mandated), which will by itself require a quantum increase in vehicle size/weight.
I suspect that the French wouldn't have bothered with such an intermediate and short/lasting solution and would have accepted moving straight to a 2-man long 47 turret light infantry tank, if that class is to remain. Both solutions would have required severe changes in technology (engine*) and/or logistical class to cope. This would mostly be a matter of figuring out if an intermediate logistical weight class between 20 and 35 tonnes (the existing thresholds) could be devised.

Agreed. The 37mm Fortress gun needs to be reworked. Like a lot of ex-naval guns it is heavy and not balanced for use in a tank. Both of these can be solved but that adds to the time in development before a useable gun is fielded. The ammo and gun are both larger than the US 37mm gun. I agree that trying to use this in a one man turret is going to be very hard and may require a 2 man turret, and if you are going to make a new two man turret, make it big enough to hold a larger gun. The 47 SA 35 looks promising. 3-4 time the HE of 37mm shell and perhaps room for 'trick' AP. Trying to use the 650mm longer tube of the towed AT gun (and it's greater weight and larger ammo) in a 'light tank' may be asking a bit much. Depends on definition of of light tank. The towed AT gun is very close to the German 5cm Pak 38 so I would judge accordingly. If somebody wants the traditionally heavy French armor the bigger gun may have to go.

*while the 1-man turret future light tanks were presently mooted with 200-230 hp class straight-six engines with potential for more power if fully developped, such upscaled tanks might instead benefit from the lower end of the battle tank engines in development in 1939 with 340 hp, as the battle tank class had itself moved to beyond 400 hp with slightly enlarged derivatives of these engines in 1940.

It also takes time to sort out the engines, especially once we start leaving truck/bus engines behind.

The development timeframes can be a little skewed by the fact most French tank types in service in 1940 were introduced in 1935/36 while we will never know for sure when the successors would have actually been fielded. But other than particular cases, it wasn't really much slower than other countries.

That is all true and as we know from the British tank development history, trying to compress the time can bite you in the ass.
German MK III & IV worked as well as they did (and they weren't really that great) because they had several years of peacetime development AND they ordered batches of 10-35 tanks at once (actual delivery was slow) to sort out problems rather than batches of 1-3 prototypes. Trying to sort out new engines, transmissions, suspensions AND guns, turrets etc etc after people are shooting at you gets hard.
US sometime cheated. For the Medium tanks they just 3 bogies instead of 2 over simplified but in 1940 they were not trying to re-invent the wheel unless absolutely necessary. They still mucked up a few things.

 

[Shortround6]

Going back to the British and the 2pdr, it seems this is a timeline for the Ammo.

AP shell.................................1934
AP shot..................................1936
HE............................................1938
APC.................................May 1942
ABCBC............................Aug 1942
APHV.............................Sept 1942
APCR................................Jan 1943

Now please note that the 6pdr Crusader shows up in North Africa just in time for El Alamein in Oct 1942. Production add started in May 1942 and 144 were complete by July but since you had to ship them around Africa and then get them ready for service and actually train with them for at least a few days. Unfortunately the manufacture and shipment applies to ammo also. By the time the better 2pdr ammo shows up not only are the 6pdr Crusaders arriving, the 6pdr AT guns are already there and the Grants have been in use for months and the Shermans are going into service at about the same time. Too little, too late pretty much covers the improved 2pdr ammunition. A post script detailing the court marshals of those responsible would have been interesting. The US managed to get APCBC ammo for the 37mm guns sooner and since they didn't even adopt the gun until Dec 1938 and first production gun showed up in July 1940 it does seem the British were not only dragging their feet, they had nailed their shoes to floor.
There are some comments/complaints about HE ammo and capped ammo being longer and not fitting in some of the storage bins. But not all storage bins had to fit all types of ammo and there were several years to short that type of thing out. Tell the designers that they needed to provide X percent of ammo bins to hold a longer round. So far no satisfactory answer to the lack of HE round, in fact it seems to be worse. They had one, they just didn't order in numbers and didn't issue it to the troops or not in any numbers that troops remembered.
Was it low powered for an HE round, yes, but no worse than the HE rounds used by the French, the Germans, the Czechs, the Americans, the Japanese and others.
HE rounds are useful for things other than dug in AT guns and fortifications. They are useful for troops in concealment, for troops in lightly constructed buildings, for artillery in the open, for trucks/motor transport. Yes you can use the co-ax machine gun for many of these targets but being able to use even small HE adds to the effect. It seems that the tanks did NOT have specialized machine gun ammo, or at least not much. In 1942 or after the troops were asking for more AP, incendiary and tracer ammo. AP was somewhat useful for shooting through gun shields. Incendiary was useful for shooting up trucks/non armored vehicles. And if you don't have HE cannon ammo what else can you use?
Cruiser tanks were supposed to get into the enemies rear areas and attack more exposed parts of the enemy army than they would find in the front lines. The more mayhem they could do in a short period of time had a better chance of routing the enemy troops and really disrupting things. Not issuing HE ammo certainly seems counter productive even if it doesn't work well on pill boxes or dug in weapons pits.
How well does AP shot work on fortifications ?
After 2 years since the Battle of France starts the British had made zero improvements to both the AP ammo situation and the HE situation.
Or to the doctrine of shooting while moving (or at least not much).
But the 2pdr gets most or all of the blame.
Soviets might have loved having 2pdr HE ammo for their Matildas and Valentines.

British tank production was a mess. They didn't stop Matilda production until Aug 1943.
Not getting into if the Matilda was good or bad but at times the British had 5-6 tanks armed with 2pdr guns in production at the same time (does not include armored cars).
And for a lot of that time the Plain AP shot was the only round being distributed for it. If they don't fix that there wasn't a lot of sense building new guns with similar restricted ammo.
Troops in NA had 6pdr AT guns, they knew 6pdr armed tanks were coming, they were asking for 6pdr capped shot or capped ballistic capped shot and HE ammo before the tanks showed up at the docks.

 

[tomo pauk]

There are some comments/complaints about HE ammo and capped ammo being longer and not fitting in some of the storage bins. But not all storage bins had to fit all types of ammo and there were several years to short that type of thing out. Tell the designers that they needed to provide X percent of ammo bins to hold a longer round. So far no satisfactory answer to the lack of HE round, in fact it seems to be worse. They had one, they just didn't order in numbers and didn't issue it to the troops or not in any numbers that troops remembered.

Outrageous, all the way.

Soviets might have loved having 2pdr HE ammo for their Matildas and Valentines.

Rumor has it that Soviets were removing the AP shots from the 6pdr cartridges for their Valentines and Churchills and retrofitting their 57mm HE shells, since the number of Britsh HE shells was very small % of the 6pdr ammo provided.

British tank production was a mess. They didn't stop Matilda production until Aug 1943.

There were thousands of British tanks very deserving of the hatchet before people look to Matlilda II sideways.

 

[Shortround6]

Outrageous, all the way.

agree, obviously

Rumor has it that Soviets were removing the AP shots from the 6pdr cartridges for their Valentines and Churchills and retrofitting their 57mm HE shells, since the number of Britsh HE shells was very small % of the 6pdr ammo provided.

interesting.

There were thousands of British tanks very deserving of the hatchet before people look to Matlilda II sideways.

I would agree, the point is they were making too many different types. With the Matilda II, Valentine, and Churchill all offering the same gun, roughly the same speed and around the same armor at the same time. Only real difference was the amount ammo carried and the extra machine gun in the Churchill and that increase in "fighting power" was not great (more in the minds of the designers/committee) They got around to increasing the gun and armor of the Churchill..........eventually.
Using the infantry tanks as ersatz cruisers is really admitting they had screwed up the cruiser tank implementation in spectacular fashion. We can argue about the doctrine, specification but the supplied tanks didn't have the reliability to perform the mission. Sending the Cruisers into the enemy rear areas to force him to retreat doesn't work well when most of your tanks are going to breakdown before they shoot up very much rear area "stuff" (supply dumps, head quarters, heavy artillery and so on). Not much enemy AT gun or counter attack by enemy tanks needed. British Cruiser tanks were not capable of staying running in large numbers over 200-300 miles of movement.