Tank & AFV armament alternatives, 1935-45

[Shortround6]

Valentine is a bargain. When 1st available, it was half a price of the Matilda II with the same gun, and just a slightly less armor thickness.

Part of the bargain was the lower combat value.
The Matilda had a 4th crewman from the start, not until the Valentine MK III did they get 3 man turret, which was after 1800 of the 2 man turret tanks were built.
The Matilda carried more main gun ammo, about 17% more.
It had better vision for commander, not much, but anything was an improvement.
The Matilda had more range.
The Valentine was a better value, you did not the same combat capability for 1/2 the price.

And two tanks to carry almost the same amount of ammo into battle as a single larger tank is seldom the bargain it appears. A tank is a tank may appeal to the accountants but trying to deal with lots of tanks that carry a small war load and need either replenishment on site or need to withdraw from the battle for replenishment complicates logistics/battle planning. Lots of small cheap tanks shuttling in and out of the battle to replenish means how many actually fighting the battle at any one time? Granted there were times when Shermans had to leave a fight in order to replenish.

In the 1930s you have to deal with doctrine/requirements and little or no combat experience. Or little post WW I experience.
British MK IV male tanks carried up to 332 rounds for their two 6pdr guns. Really makes one wonder about the lack of HE support from the 2pdr armed tanks. German MK IIIE with 37mm carried up to 131 rounds of 37mm (granted a mix of AP and HE) and 4500 rounds of machine gun ammo.

 

[EwenS]

The origins of Valentine go back to the beginning of 1938. Vickers had designed the A11 Matilda I to meet a War Office Spec as well as the A9 & A10 cruisers. It realised it could build a compact infantry tank with a crew of 3 using the components of the latter and with an eye on the potential export market. So Valentine was a private venture, not the product of a formal WO spec.

The design team set to work designing a tank using an A10 chassis reinforced to carry 16 tons (which they knew would be reliable) and designed to use Vickers production processes for rapid production (estimate was two thirds the build time of an A12 Matilda II).

Knowing that armour thickness had a habit of growing, they started at 60mm (double that of the A10 cruiser). But with the limited weight budget it couldnt be large, and other sacrifices had to be made (no cupola, one man in hull). Vickers also wanted to use their own 40mm automatic gun with the same ammunition, as the WO weapon, which was fiercely resisted by the WO.

The War Office wanted Vickers to produce the, then as yet unbuilt, A12 Matilda II. After due consideration of a mock up between Feb-Mar 1938 the WO rejected the Vickers proposal for a variety of reasons. Despite that Vickers continued to work on the design.

April 1939 the WO resurrected discussions and we're prepared to accept a 2 man turret if production could begin rapidly, but wanted other changes. From that meeting came an tentative order for 100 (reduced to 50 in actual contract at the beginning of July), followed by orders for 2 other companies at the end of June for 125 each.

Vickers were able to deliver the first production Valentine for testing in late April 1940.

 

[EwenS]

Just for fun
View attachment 808543

This looks like the 7.92" mortar carrier. Designed to project chemical munitions or a 25lb incendiary bomb. Trialled at the Petroleum Warfare Establishment 1943-45 but not developed further.

 

[Shortround6]

This looks like the 7.92" mortar carrier. Designed to project chemical munitions or a 25lb incendiary bomb. Trialled at the Petroleum Warfare Establishment 1943-45 but not developed further.

yes, it just looks cool with the semi mushroom cloud in the background.

 

[tomo pauk]

Part of the bargain was the lower combat value.
The Matilda had a 4th crewman from the start, not until the Valentine MK III did they get 3 man turret, which was after 1800 of the 2 man turret tanks were built.
The Matilda carried more main gun ammo, about 17% more.
It had better vision for commander, not much, but anything was an improvement.
The Matilda had more range.
The Valentine was a better value, you did not the same combat capability for 1/2 the price.

Similar math was in effect when we compare KV-1 and T-34. It was far worse when the M3 Medium or M4 were compared with M3 light and M5. Same when Pz-III was compared with Pz-II.
Every army in the day would've loved the multi-purpose tanks with heavy armor, great firepower and great mobility. Same as with every Western airforce would've just loved the F-15 between 1975 and 2000. Reality was different, everyone was making simpler, cheaper and less capable jets in that time, and the people were buying the less capable tanks even when the better/best (at least on paper) were in the pipeline.

And two tanks to carry almost the same amount of ammo into battle as a single larger tank is seldom the bargain it appears. A tank is a tank may appeal to the accountants but trying to deal with lots of tanks that carry a small war load and need either replenishment on site or need to withdraw from the battle for replenishment complicates logistics/battle planning. Lots of small cheap tanks shuttling in and out of the battle to replenish means how many actually fighting the battle at any one time? Granted there were times when Shermans had to leave a fight in order to replenish.

Look at this from the high command PoV in the 1930s. Unless they are the French or Soviets, they need to create the armored divisions often from nothing. Opting for the bestest tank will mean that better half of the armored divisions required is outfitted with armored cars instead of the tanks.

In the 1930s you have to deal with doctrine/requirements and little or no combat experience. Or little post WW I experience.
British MK IV male tanks carried up to 332 rounds for their two 6pdr guns. Really makes one wonder about the lack of HE support from the 2pdr armed tanks. German MK IIIE with 37mm carried up to 131 rounds of 37mm (granted a mix of AP and HE) and 4500 rounds of machine gun ammo.

Not making the retrograde step with the adoption of the 3pdr would've been a good idea.
Send to the Falklands anyone who suggests the not issuing HE shells to the tanks, and to the South Georgia the one that suggests that 2pdr is a good tank gun.

 

[Snautzer01]

Same as with every Western airforce would've just loved the F-15 between 1975 and 2000

No. Too expensive. Not in enveloppe of need by eu airforces then. They should have, but politics said no.
You are not in the army to love things.

Now, in these days, perhaps budgets would have made room. It is a good platform still.

 

[Shortround6]

Similar math was in effect when we compare KV-1 and T-34. It was far worse when the M3 Medium or M4 were compared with M3 light and M5. Same when Pz-III was compared with Pz-II.
Every army in the day would've loved the multi-purpose tanks with heavy armor, great firepower and great mobility. Same as with every Western airforce would've just loved the F-15 between 1975 and 2000. Reality was different, everyone was making simpler, cheaper and less capable jets in that time, and the people were buying the less capable tanks even when the better/best (at least on paper) were in the pipeline.

True but the light tanks were not a great bargain. Trade offs are made and having fewer tanks for the same money does not look good to the accountants. Having poor tanks is often (but not always) better than no tanks in certain areas while the better ones were somewhere else. The whole idea of infantry support tanks with every infantry division getting a company or battalion of tanks but having no actual tank divisions. Not a wise choice for how to spend money.

Look at this from the high command PoV in the 1930s. Unless they are the French or Soviets, they need to create the armored divisions often from nothing. Opting for the bestest tank will mean that better half of the armored divisions required is outfitted with armored cars instead of the tanks.

French had over 1000 left over WW I tanks, they built how many hundreds of those little two man FT-17 replacements instead instead 3-4 man medium tanks to equip several armored divisions. A number of smaller countries spent way too much money on light armored vehicles (not tanks) for propaganda purposes. Italy, I am looking at you.

2500 built, repeat 2500 built.

Maybe they should have built another 100 of these instead of around 300 of the little ones

Still crap but not as crappy. At least it would have some chance against a RR armored car

Not making the retrograde step with the adoption of the 3pdr would've been a good idea.
Send to the Falklands anyone who suggests the not issuing HE shells to the tanks, and to the South Georgia the one that suggests that 2pdr is a good tank gun.

While the 1920s 3pdr may not have been the best idea it beat the heck out keeping the old 6pdrs.

1,350 ft/s (411 m/s) MV. These things were pretty much ex black powder guns (or close to it) using HE shells filled with black powder.
The 1920s 3pdr guns would actually go through more armor. Not much but they would. They were also easier to hit with their higher velocity, higher being relative but they at least had a point blank range about that of the 75mm field guns. Requirement was to penetrate the armor of the expected enemy tanks at 1000yds. Now this was in 1928 so nobody had thick armor. Getting a hit at 1000yds was a lot easier than using the old sawed off guns.
Using the old guns with the original length barrels even in the 1930s was going to get you much.
2pdr AT gun= 337,782 joules (original load)
3pdr tank gun = 231,000 joules
6pdr short gun = 230,000 joules (WW I late)
6pdr long gun = 397,000 joules (WW I early)
The old guns are going to weigh a lot more and the ammo will take up more room (less of it in a given size tank)


Now to criticize the 2pdr as a tank gun we also have to criticize everybody who who used/adopted 37-47mm guns in their tanks. Although sending the person/s responsible for the no HE ammo for the 2pdr guns the South Georgia location plan is too kind. Dartmoor prison was a more fitting location.

 

[bf109xxl]

Valentine is a bargain. When 1st available, it was half a price of the Matilda II with the same gun, and just a slightly less armor thickness.

Not "slightly" - 75 mm vs 60 mm is a significant difference. The Soviets considered the Matilda II as almost equal to the KV by armoring (and highly respected for this) - even with less thickness, British armor provided similar protection due to a higher quality. In 1940, the Valentine was approx. 20% cheaper to build than the Matilda.

 

[yulzari]

And what happens when you have average gunners?
Not poor, just rushed in building up desired forces.

And what happens at longer ranges?
Like much over Point Blank when putting the cross hairs just over the enemy target is no longer enough.

What happens at the longer ranges when the average gunner needs repeat shots and can't just dial the elevation up or down, even with the tank sitting still?

British used a lower magnification sight, perhaps to allow for a wider field of view for shooting on the move.
But this meant more difficulties shooting at long range.
By the way, in desert long range for 2pdr armed tanks was anything much over 800 yds. Maybe the expected ranges in France were less but they shot themselves in both feet with this one and kept throwing the crutches away for several years. Apparently I was in error earlier about shoulder control being used with close support howitzers. The Chieftain's video of the A10 CS tank shows hand wheel elevation for the 3.7in Mortar. Never let actual experience get in the way of good doctrine, or even mediocre doctrine........................heck, even down right crappy doctrine.

It was trialled and used and found effective. It was, however, an answer for a brief window but eventually abandoned as weights rose and it became impractical. I was not arguing for it but noting how to came about and why it was a practical option at the time. The doctrine was founded upon naval practice and applied to the 2 Pounder and preceding 3 Pounder and was an option with the 6 Pounder. The Crusader 6 Pounder having free elevation and the Churchill geared. I recognised the negative impact upon the gun/turret interface with the internal mantlet (mounted upon the gun mount) with it's large hole on the turret face armour and space to work, recoil and elevate the breech.

A brief moment in time when it had some merit and gave gunners the chance to fire as a moving platform whilst the enemy were constrained to stop to fire making them an easier target. So it was not a daft idea but a limited one.

 

[tomo pauk]

True but the light tanks were not a great bargain. Trade offs are made and having fewer tanks for the same money does not look good to the accountants. Having poor tanks is often (but not always) better than no tanks in certain areas while the better ones were somewhere else. The whole idea of infantry support tanks with every infantry division getting a company or battalion of tanks but having no actual tank divisions. Not a wise choice for how to spend money.

This is where the Valentine shines, and even more a 'proper' 18-20 ton tank. Making more of them instead of the light tanks is/was a way to go. Unfortunately for the historical British tanks arm, Valentine was too late for the pre-1940 build-up.

While the 1920s 3pdr may not have been the best idea it beat the heck out keeping the old 6pdrs.
1,350 ft/s (411 m/s) MV. These things were pretty much ex black powder guns (or close to it) using HE shells filled with black powder.
The 1920s 3pdr guns would actually go through more armor. Not much but they would. They were also easier to hit with their higher velocity, higher being relative but they at least had a point blank range about that of the 75mm field guns. Requirement was to penetrate the armor of the expected enemy tanks at 1000yds. Now this was in 1928 so nobody had thick armor. Getting a hit at 1000yds was a lot easier than using the old sawed off guns.

Use the 6pdrs with normal barrel lengths in the 1920s - these were good for 538 m/s as-is, ie. no worse than the field guns of the day - and see that can be done to improve the AP performance.
Move to the higher-power 6pdrs or/and 12-13 prd guns by the mid-1930s.

Using the old guns with the original length barrels even in the 1930s was going to get you much.
2pdr AT gun= 337,782 joules (original load)
3pdr tank gun = 231,000 joules
6pdr short gun = 230,000 joules (WW I late)
6pdr long gun = 397,000 joules (WW I early)
The old guns are going to weigh a lot more and the ammo will take up more room (less of it in a given size tank)

I want quality, so the original length 6pdr is simply great.
BTW - the 2 pdr scores zero points for the HE ability, same for the 3pdr. Even if we stick the HE shells on these guns, one 6 pdr shell is worth perhaps as much as three 2 pdr shells, or as much as two 3 pdr shells; I'm being conservative on purpose here. A tank that the 6pdr hits will be most likely destroyed, together with it's crew (sorry, folks), while the 2 pdr will require a few additional hits to do the same.
We also have a thing that British have all of the 1930s to start designing and debugging the tanks with the better abilities if they start with the 6 pdr, that also makes the path to the further upgrades of firepower easy job.

Now to criticize the 2pdr as a tank gun we also have to criticize everybody who who used/adopted 37-47mm guns in their tanks.

We do not.
French were moving from 37mm to 47mm (so it is a step up), and their 47mm guns were issued with HE shells. French were also installing the most powerful 75mm guns on the tanks of 1930s, whose purpose was both for AP and HE. It will take until 1941 for someone to beat them in that game; it will take the British until 1943 to beat the French in the installation of a 75mm gun on a tank.
Both Soviets and Germans were issuing the 75-76mm guns on the tanks in the late 1930s (Soviets even earlier), and their small guns on the tanks were still with the HE shells. Germans were making the StuG-IIIs with the 75mm gun; yes, it was not a tank.

Nobody else was saying: okay, now that we have a 20-30 ton tank, putting the very small gun on it is the greatest idea.

 

[Shortround6]

A brief moment in time when it had some merit and gave gunners the chance to fire as a moving platform whilst the enemy were constrained to stop to fire making them an easier target. So it was not a daft idea but a limited one.

You are correct but the choice was there and the choice was between short range fire and long range fire. Each path had limits and each had terrain areas it could shine in.
While the geared elevation was slower at short range it did not really prohibit firing at short range. The free elevation (shoulder) piece did not prohibit firing at long range but it required a much larger expenditure of ammunitions to get a hit, required firing while stationary and in a 10 tank on 10 tank dual/engagement the geared elevation tanks were going to get more hits sooner in the exchange and the balance is going to shift in their favor very quickly. If the powers that be thought they would never have to shoot at long range then perhaps the right choice at the time.

 

[Shortround6]

This is where the Valentine shines, and even more a 'proper' 18-20 ton tank. Making more of them instead of the light tanks is/was a way to go. Unfortunately for the historical British tanks arm, Valentine was too late for the pre-1940 build-up.

Well, the Valentine is late and it won't really do the cruiser tank job but that is a story for another thread.

Use the 6pdrs with normal barrel lengths in the 1920s - these were good for 538 m/s as-is, ie. no worse than the field guns of the day - and see that can be done to improve the AP performance.
Move to the higher-power 6pdrs or/and 12-13 prd guns by the mid-1930s.

More on this later but the 6pdr was over 3 times as heavy as the 2pdr.

I want quality, so the original length 6pdr is simply great.

Actually it was a rather poor hole puncher.
gun.......................size hole.................Joules......................joules per sq cm
2pdr.....................40=12.566............337,782.....................26,880
3pdr.....................47=17.35..............231,000......................13,314
6pdr (S)..............57=25.52...............230,000........................9,020
6pdr (L)..............57=25.52...............397,000......................15,556
German 37.......37=10.752.............200,000......................18,000

BTW - the 2 pdr scores zero points for the HE ability, same for the 3pdr. Even if we stick the HE shells on these guns, one 6 pdr shell is worth perhaps as much as three 2 pdr shells, or as much as two 3 pdr shells; I'm being conservative on purpose here. A tank that the 6pdr hits will be most likely destroyed, together with it's crew (sorry, folks), while the 2 pdr will require a few additional hits to do the same.
We also have a thing that British have all of the 1930s to start designing and debugging the tanks with the better abilities if they start with the 6 pdr, that also makes the path to the further upgrades of firepower easy job.

Sorry, any tank with decent armor (30mm) is not going to be taken out with 57mm/6pdr HE ammo. disabled maybe. 30mm armor at the time was considered "shell proof" that is 75mm field gun HE ammo could not hurt (nothing is said about hearing loss) what was inside the tank.

We do not.
French were moving from 37mm to 47mm (so it is a step up), and their 47mm guns were issued with HE shells. French were also installing the most powerful 75mm guns on the tanks of 1930s, whose purpose was both for AP and HE. It will take until 1941 for someone to beat them in that game; it will take the British until 1943 to beat the French in the installation of a 75mm gun on a tank.
Both Soviets and Germans were issuing the 75-76mm guns on the tanks in the late 1930s (Soviets even earlier), and their small guns on the tanks were still with the HE shells. Germans were making the StuG-IIIs with the 75mm gun; yes, it was not a tank.

Nobody else was saying: okay, now that we have a 20-30 ton tank, putting the very small gun on it is the greatest idea.

A really big problem is that most people were were not designing 20-30 ton tanks.
Or if they were the results did not look good.

That is the short 47mm gun. 19.75 metric tons, speed 23kph. Or

76.2mm HE round had a MV of 262m/s

Actual photos of the T-26-4 seem scarce. Of course the Soviets were building light tanks with twin turrets

either a mg in each turret or a short 37mm in one turret and a mg in the other. Machine guns were pretty much the 'go to' solution for soft targets.
Lack of actual experience?

The 2pdr gun itself was not bad, the decisions not to give it HE ammo, capped ammo and geared elevation/better sight is what crippled it in use in 1939-41 and if you put those limitations on any other caliber weapons you would have suffered similar results.

 

[tomo pauk]

More on this later but the 6pdr was over 3 times as heavy as the 2pdr.

As one can expect, since it was a decades older design.

Actually it was a rather poor hole puncher.
gun.......................size hole.................Joules......................joules per sq cm
2pdr.....................40=12.566............337,782.....................26,880
3pdr.....................47=17.35..............231,000......................13,314
6pdr (S)..............57=25.52...............230,000........................9,020
6pdr (L)..............57=25.52...............397,000......................15,556
German 37.......37=10.752.............200,000......................18,000

There are years available to make better ammo, as well as a new gun with even better ammo.
As I'v suggested a few times in the other thread.

A really big problem is that most people were were not designing 20-30 ton tanks.

No, the most capable people in the most capable companies were the ones were tasked for designing 20-30 ton tanks.

Sorry, any tank with decent armor (30mm) is not going to be taken out with 57mm/6pdr HE ammo. disabled maybe. 30mm armor at the time was considered "shell proof" that is 75mm field gun HE ammo could not hurt (nothing is said about hearing loss) what was inside the tank.

Hopefully, British tankers will recall that the enemy tank should be fired at with the AP shot, not the HE shell.

 

[tomo pauk]

Options for the Soviets:
- keep making and installing the 57mm gun on the T-34 in some decent quantities
- adopt the best part of the F22 gun for the T-34 and KV-1, as well as the hot loaded ammo (1400g of propellant vs. 1080g in the 'normal' AP & APHE ammo); should be getting to perhaps 730+ m/s with the 6.3-6.5 kg AP ammo (French were getting max 715 m/s with the 1250g propellant load and the ~6.2 kg shell on their AA pieces, and less with 6.4 kg shell), and probably over 1050 m/s with the APCR



- install the 85mm gun on the SU-122 chassis by winter of 1942/43, the SU-122 remaining a prototype only
- 100 mm gun on the KV and IS tanks
- make a not-SU-122 (cannon-armed) instead of the SU-152 on the KV chassis
- have the T-43 to be designed with an 85mm gun from the get go

Soviets have had perhaps the best choice of guns, but the installation of these on the tanks and AFVs was many times lagging behind the needs. Granted, being trashed by the Germans in the 1st 18 months of the war meant that good tanks were preferred, not the best possible stuff

 

[z42]

Options for the Soviets:
- keep making and installing the 57mm gun on the T-34 in some decent quantities
- adopt the best part of the F22 gun for the T-34 and KV-1, as well as the hot loaded ammo (1400g of propellant vs. 1080g in the 'normal' AP & APHE ammo); should be getting to perhaps 730+ m/s with the 6.3-6.5 kg AP ammo (French were getting max 715 m/s with the 1250g propellant load and the ~6.2 kg shell on their AA pieces, and less with 6.4 kg shell), and probably over 1050 m/s with the APCR

View attachment 808667

- install the 85mm gun on the SU-122 chassis by winter of 1942/43, the SU-122 remaining a prototype only
- 100 mm gun on the KV and IS tanks
- make a not-SU-122 (cannon-armed) instead of the SU-152 on the KV chassis
- have the T-43 to be designed with an 85mm gun from the get go

Soviets have had perhaps the best choice of guns, but the installation of these on the tanks and AFVs was many times lagging behind the needs. Granted, being trashed by the Germans in the 1st 18 months of the war meant that good tanks were preferred, not the best possible stuff

Was there something majorly wrong with the L-11 and F-34 76mm guns in the early-mid war? Seems to me the guns themselves were ok, what would have been needed was a 3-man turret for the T-34 from the outset, a radio in every tank, and much better training and tactics.

Sure, at some point the Germans start showing up with heavier tanks, and these guns are no longer adequate. So, as historical, switch to the 85mm? And then the 100mm; the 122mm was arguably unnecessary at that point.

 

[tomo pauk]

Was there something majorly wrong with the L-11 and F-34 76mm guns in the early-mid war? Seems to me the guns themselves were ok, what would have been needed was a 3-man turret for the T-34 from the outset, a radio in every tank, and much better training and tactics.

If they go with the more powerful 76mm gun, that removes the (presumed?) need to install the 57mm on the T-34s.
Already by Spring of 1942, the T-34s were being out-gunned by the Pz-IVF2/G and Stug-IIIF, and probably by the Pz-IIIJ. The different SP tank busters were also started to be deployed in that time. All of them, bar the IIIJ, will be able to destroy a T-34 at 1500m, and the IIIJ might do it at 1000m.

Granted, the T-34 will need a lot more to improve on in order became the tank it was supposed to be.

Sure, at some point the Germans start showing up with heavier tanks, and these guns are no longer adequate. So, as historical, switch to the 85mm? And then the 100mm; the 122mm was arguably unnecessary at that point.

The move towards the 85mm needs to start by the late 1942, perhaps spurred by the encounter with the Tiger tanks in that time? So the 1st tanks/AFVs can be in the units by Spring of 1943, hopefully.

 

[bf109xxl]

- keep making and installing the 57mm gun on the T-34 in some decent quantities

Based on the results of the Battle of Moscow, the use of the T-34 with 57 mm ZIS-4 gun was considered unsatisfactory - the task range became narrower, the effectiveness of fire on infantry and fortifications became much worse, so further use of this gun on the T-34 was abandoned. In 1943, under desperate circumstances it was decided to install it again, but it quickly came to the same conclusions. Anti-tank functions were transferred to the self-propelled artillery (which Soviet commanders, due to insufficient understanding of tactics, persistently used as tanks). Soviet ZIS-5 and F-34 guns were fully adequate until late 1942. And even later - under condition of the availability of high quality AT shells.

- adopt the best part of the F22 gun for the T-34 and KV-1...

What does that mean? What makes you sure that the result could be fit in the turret of a T-34? How does this differ from increasing the length of the F-34 barrel to 60 caliber when using a shell from a 3K anti-aircraft gun with an enhanced charge, i.e. the C-54? The Soviets equipped about 100 T-34s with these guns, and armor penetration was greatly increased, but as it turned out, there were too few Tigers to justify the double cost of the round. In addition, experts at the Aberdeen Proving Ground believed that the F-34 could have a muzzle velocity of about 850 m/s already only if better powder was used.

, as well as the hot loaded ammo (1400g of propellant vs. 1080g in the 'normal' AP & APHE ammo); should be getting to perhaps 730+ m/s with the 6.3-6.5 kg AP ammo (French were getting max 715 m/s with the 1250g propellant load and the ~6.2 kg shell on their AA pieces, and less with 6.4 kg shell), and probably over 1050 m/s with the APCR

And why would it be necessary, if the cartridge case of 76-mm and 85-mm is the same? Given this fact, the 85mm gun was a better solution for the T-34.

- install the 85mm gun on the SU-122 chassis by winter of 1942/43, the SU-122 remaining a prototype only

Actually, the chassis of the SU-122 was completely taken from the T-34. And the most important thing, it is not clear why SU-122 and SU-85 are opposed at all, if they had different targets and objectives on the battlefield. The main task of SU-122 was suppression of enemy artillery (first of all - anti-tank), for this purpose a powerful HE shell was required. SU-85 is primarily an anti-tank weapon. Both of these self-propelled guns were required by tank units.

- 100 mm gun on the KV and IS tanks

And why not 107mm? And why a 100mm gun was better than the 122mm D-25, which the IS received in reality? In 1941 an 85-mm gun (U-12) was tested on the KV, and even its installation was considered unjustified at that time - it was too expensive. KV-2 with 107-mm was also tested with the same result. There was no need for a tank with such a gun in 1941. And even in 1942 it was not needed yet. And in the fall of 1942, when the factories were able to start production of a new tank, and the need for it became more obvious, the Stalingrad crisis occurred, which crossed out most of the alternatives - quantity was required.

- make a not-SU-122 (cannon-armed) instead of the SU-152 on the KV chassis

Why? What exactly was wrong with the ML-20? Why to make a self-propelled gun when there was a tank with 122-mm gun? The IS with 122-mm gun was mass-produced from December 1943.

- have the T-43 to be designed with an 85mm gun from the get go

The Battle of Kursk was necessary to realize the necessity to equip the tank with an 85 mm gun. The D-5T (modified U-12) appeared only in May 1943, and it was not optimal for the tank. ZIS-S-53 was created by order from the end of October 1943, it was produced since February 1944, it is difficult for me to conclude whether it could have been developed and put into production earlier. The T-43 did not require any serious modifications of the hull (and perhaps the turret as well) to mount the 85 mm gun - the tank had already an increased turret ring with a diameter of 1600 mm.

Soviets have had perhaps the best choice of guns, but the installation of these on the tanks and AFVs was many times lagging behind the needs. Granted, being trashed by the Germans in the 1st 18 months of the war meant that good tanks were preferred, not the best possible stuff

The Soviets tried not to use tanks as anti-tank weapons - heavy tanks were to break through defense lines, medium tanks (including the Valentine, which was widely used in cavalry corps) were to be brought into a breakthrough and used as cruiser tanks, and light tanks were to support infantry directly. The Soviets had an almost ideal light tank for infantry support - the T-50 with the 45-mm 20K (a 57-mm gun should be install later), but at the beginning of the war its serial production had not been started, and in the conditions of the war and evacuation of factories it was unrealistic to deploy production of a new engine (V-4), so only about 70 T-50s were produced. For a number of reasons, it was not possible to produce an alternative GMC engine, moreover, the Valentines received under Lend-Lease were considered to be comparable to the T-50. Perhaps this was the only alternative that could be realized.

The Soviets, I believe, had no conceptual problems, but they had a great shortage of qualified engineering stuff, a low technological level, and a limited production flexibility, exacerbated by the use of low-skilled labor. Even if the Soviets had a crystal ball in which they could see the future, it is doubtful that even this knowledge would have been able to change anything fundamentally.
Moreover, the Soviets' major problems, I believe, were not technical at all. If you use SU-76s as tanks and suffer huge losses, no technical solutions can compensate for tactical illiteracy.

 

[bf109xxl]

Was there something majorly wrong with the L-11 and F-34 76mm guns in the early-mid war?

The L-11 was unreliable and more complicated in use. The major problem of Soviet guns was the lack of an adequate armor-piercing shell or its poor quality.

Seems to me the guns themselves were ok, what would have been needed was a 3-man turret for the T-34 from the outset, a radio in every tank, and much better training and tactics.

I've already pointed this out above.

Sure, at some point the Germans start showing up with heavier tanks, and these guns are no longer adequate. So, as historical, switch to the 85mm? And then the 100mm; the 122mm was arguably unnecessary at that point.

I have to repeat once again: fighting enemy tanks was not the main task of Soviet tanks. And the caliber of the guns was not chosen only taking into account armor penetration.

 

[bf109xxl]

If they go with the more powerful 76mm gun, that removes the (presumed?) need to install the 57mm on the T-34s.

The Soviets did not need more powerful 76mm gun as they used the same cartridge case for both 76mm and 85mm rounds.

Already by Spring of 1942, the T-34s were being out-gunned by the Pz-IVF2/G and Stug-IIIF, and probably by the Pz-IIIJ. The different SP tank busters were also started to be deployed in that time. All of them, bar the IIIJ, will be able to destroy a T-34 at 1500m, and the IIIJ might do it at 1000m.

It wasn't crucial. The difference was small; until the Tigers appeared, the Soviets did not see a big problem. And once again: using tanks as anti-tank weapons was considered a serious mistake according to Soviet tactics.

Granted, the T-34 will need a lot more to improve on in order became the tank it was supposed to be.

That can be said about any tank.

The move towards the 85mm needs to start by the late 1942, perhaps spurred by the encounter with the Tiger tanks in that time? So the 1st tanks/AFVs can be in the units by Spring of 1943, hopefully.

In the fall of 1942, the Soviet tank industry was in crisis due to the loss of the Stalingrad plants. The transition to 85mm guns (which did not appear until May 1943) was impossible.

 

[Shortround6]

There are years available to make better ammo, as well as a new gun with even better ammo.
As I'v suggested a few times in the other thread.

There are 3 ways to make 'better' AP ammo.
1. Make better AP shot (better heat treatment, add piercing cap, add ballistic cap, change weight)
2. Increase velocity (new powder, higher pressure, larger chamber/more powder)
3. Change type of projectile (HEAT, APCR, etc)
Some of these are somewhat time dependent. When do the better powders show up? When did HEAT (shaped charges show up).
Sometimes you can make a better new gun/ammo than trying to up grade an old gun to do about the same thing. Both steel and powder technology were advancing in the 20s and 30s. Picking an older gun with the idea it can be modified or upgraded at a later date instead of designing a new gun that pretty much does what you want (velocity for weight of gun)
may not have been a good idea.

No, the most capable people in the most capable companies were the ones were tasked for designing 20-30 ton tanks.

Some of the ones designing 30 ton tanks had the best lobbyists

In the 1930s a lot of countries didn't know what the best solution/s were. It took quite a while (1945?) to arrive at point where most people agreed, 4 man crew, no bow gun, one big (or biggish gun) single co-ax gun and a few other things like good vision and good radios. There was still agreement on speed and range

It took quite a while build the best tank and NOT worry about the price (too much). Just about all the between war tanks were built to budgets, at least the ones ordered in more than one offs or very small prototype batches.

In the design phase guns are not interchangeable. If you use a larger/heavier gun you can increase the turret weight by around 3 times weight of the bare gun, (naval men said you had to cube the size of the gun). If you triple the weight of the gun you should add a bunch of weight at the rear to keep the turret in balance for easy traverse. You do need a bigger mount/elevating gear, quite possibly a bigger turret ring (not just diameter, bigger to handle the recoil load) and this may mean a longer/wider turret with increased armor weight.
Now what they manage to shoehorn in later and accept some problems may not have been acceptable in the design phase.

And some ideas were somewhat zombie like (took a lot of killing).
The British came up with this in 1925/26, 2nd appearance the of 3pdr gun?. 37 short tons. max armor 28mm

Last production appearance of the 'extra' turret was the Crusader in 1941, didn't work any better in 1941 than it did in 1925.
Now the British probably would have been better off ditching at least two of the Aux turrets and mounting a 57mm gun instead of the 47mm but this thing was so big and expensive they were never going to buy more than one unless they had a war actually going on.
Please note that the main turret did not have a machine gun so the commander in the cupola had problem directing machine gun fire on targets he wanted to engage. He somehow had to signal the appropriate gunner in the correct facing sub turret. The little turrets were basically uninhabitable when the machineguns were fired due to fumes. A problem that was unsolved 15 years later. In NA the crews solve the problem by pulling out the turrets and plating over the hole.
The British actually designed several tanks during the 20s and later 30s had the basic form of a post WW II tank. Like basic crew layout and weapons layout/configuration even if not the size/scale. They also veered back and forth several times (didn't realize what they had).

3 man turret, co-ax gun, cupola (poor one) started in 1924-26. It was far from perfect. Nearly cardboard armor, one man trying to run back and forth across the tank to man the Vickers guns out each side (one gunner/two guns). Tank in the picture had a radio in 1931-32. The MK II version got up to about 13 tons.
And this is were things do start to go wrong. Governments, trying to be cheap, tried to jam several good features into small/cheap tanks knowing they could not get everything they wanted. They often made bad choices. Or sometimes threw the baby out with the bath water (turning the Cruiser III/IV into the Cruiser V Covenantor).

The British should have spent more time fixing the things that were wrong with the Cruiser III/IV and less time trying to fix things that weren't wrong. Like the obsession with height that lead to the flat 12 engine, the squashed turret with not enough room, eliminating the cupola (granted the existing one wasn't good but you don't fix it by throwing the idea out). Lowering the hull top so you can't flare the top of the hull out to fit a bigger turret ring.

British actually did pretty good with the light tanks

Pretty much the King of the 5 ton tanks. 3 man crew. Commander was not the gunner. It had a radio (2 way!) it was zippy. It had a fair chance of killing other 5 ton and smaller tanks.
Something that could not be said of many other 5 ton tanks. Almost 1700 of them built which was the big mistake. It doesn't matter how good a light weight boxer you are when you come up against even just a competent middleweight.