Sir John Valentine Carden Survives. Part 2.

It would regardless. The 17 pounder had an HE shell as well.
The 75mm has a bigger charge.

And since we are talking about it taking on Tigers, it should be noted that the US 75 mm AP had issues with penetration and shatter gap (ie, being able to penetrate a target at 1000 yards, or 100 yards, but not in between due to the shell shattering on impact). In 1943 the ordinance board discussed the HV 75mm. Based on their tests the penetration of the HV 75 mm the with US projectile was only 87 mm at 1000 yards and 30 degrees. This is about the same as the US 76 mm (which the US Army was disappointed with) and considerably less than the 108 mm the 77 mm achieved with the same case and 17 pounder projectile. For reference, the same tests listed the 6 pounder at 76 mm with APCBC and 106 mm with Littlejohn.
Balance that out against the probability of actually meeting a Tiger. Total production was 1,347 for the Tiger I and 492 for the Tiger II, and most of both types went to the Eastern Front. Also, HEAT, HESH and sabot are going to be a thing.

IIRC (and I could have lost track of this) Allen’s HV 75 mm uses the shell from this gun rather than the US shell. Or at least the machinery. That said, most of these guns were built in Romania. Vickers did build some in Britain but as far as I can tell the last were delivered in 1939.
I doubt they scrapped the tools though.
 
It would regardless. The 17 pounder had an HE shell as well.

And since we are talking about it taking on Tigers, it should be noted that the US 75 mm AP had issues with penetration and shatter gap (ie, being able to penetrate a target at 1000 yards, or 100 yards, but not in between due to the shell shattering on impact). In 1943 the ordinance board discussed the HV 75mm. Based on their tests the penetration of the HV 75 mm the with US projectile was only 87 mm at 1000 yards and 30 degrees. This is about the same as the US 76 mm (which the US Army was disappointed with) and considerably less than the 108 mm the 77 mm achieved with the same case and 17 pounder projectile. For reference, the same tests listed the 6 pounder at 76 mm with APCBC and 106 mm with Littlejohn.


IIRC (and I could have lost track of this) Allen’s HV 75 mm uses the shell from this gun rather than the US shell. Or at least the machinery. That said, most of these guns were built in Romania. Vickers did build some in Britain but as far as I can tell the last were delivered in 1939.

You wouldn’t want to use this one directly in a tank. The shell is long and straight walled, which makes it very awkward to use in a turret and reduces the amount you can carry. I believe the HV 75 mm here uses the projectile (which I don’t know much about) with the shell from the 3” 20 cwt AA gun.
Finns used a version of the 1931 AA gun (1934) which was provided with an AP shell as well. 6.5kg 750-800 m/s muzzle velocity. The shell was 76mm x 505 R so slightly larger than the equivalent round in a Panzer IV KwK 40 L48
 
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The 75mm has a bigger charge
True. I am not sure if we have a gauge for how much is required though.

Balance that out against the probability of actually meeting a Tiger. Total production was 1,347 for the Tiger I and 492 for the Tiger II, and most of both types went to the Eastern Front. Also, HEAT, HESH and sabot are going to be a thing.
True enough. I suspect thé British will want more penetration eventually though.

I doubt they scrapped the tools though.
Possibly not. It’s definitely plausible enough that I have no objection to it being used here. Just commenting it is not necessarily as simple as plugging in the 1930’s AA gun into a tank.

Finns used a version of the 1931 AA gun (1934) which was provided with an AP shell as well. 6.5kg 750-800 m/s muzzle velocity. The shell was 76mm x 505 R so slightly larger than the equivalent round in a Panzer IV KwK 40 L48
Good point. However, the Finnish guns used 76.2 mm projectiles from more common Bofors Guns, not the Vickers ones used in other exports and produced by Vickers themselves . And the AP-T (Armour Piercing Tracer) shell used in them were likely only introduced in late 1942.
 
Good point. However, the Finnish guns used 76.2 mm projectiles from more common Bofors Guns, not the Vickers ones used in other exports and produced by Vickers themselves . And the AP-T (Armour Piercing Tracer) shell used in them were likely only introduced in late 1942.
True but the Victor isn't likely to be in full service before 1942. Of course the fact that Vickers delivered the 1931 gun in 3" as well as 75mm begs the question why they couldn't revert to 3" if the Ordnance kick up a fuss.
 
True. I am not sure if we have a gauge for how much is required though.
The M48 HE round weighed 14.9 pounds, and had a 1.47 pound charge. The 17-pounder round weighed 15.4 pounds, but onlyy had a 1.28 pound charge.

True enough. I suspect thé British will want more penetration eventually though.
Maybe, but they're going to get a while new tank in probably 1944.

Possibly not. It’s definitely plausible enough that I have no objection to it being used here. Just commenting it is not necessarily as simple as plugging in the 1930’s AA gun into a tank.
Well, a new breech certainly, maybe a few other changes too.

True but the Victor isn't likely to be in full service before 1942. Of course the fact that Vickers delivered the 1931 gun in 3" as well as 75mm begs the question why they couldn't revert to 3" if the Ordnance kick up a fuss.
More options in 75mm. A better HE round, a canister round, a white phosphorous (presumably an incendiary) round, etc. They don't need an exception AP round just yet, since Panthers won't show up until 1943.
 
More options in 75mm. A better HE round, a canister round, a white phosphorous (presumably an incendiary) round, etc. They don't need an exception AP round just yet, since Panthers won't show up until 1943.
True - you might get a 75mm / "76mm" situation similar to the Sherman though.
 
True - you might get a 75mm / "76mm" situation similar to the Sherman though.
Maybe, but the British know about HEAT already (they've known since 1940, as they captured a Panzer IV with the 75mm gun in France), and HESH is in development. APDS too, though that won't show up until they're already in France.
 
Maybe, but the British know about HEAT already (they've known since 1940, as they captured a Panzer IV with the 75mm gun in France), and HESH is in development. APDS too, though that won't show up until they're already in France.
True again. I don't think they need a 3" HV Vickers model and commonality with the Sherman 75mm base model will be a great advantage logistically. HESH might be a stretch in this calibre this early but if HEAT is receiving some love then that will definitely be deployed followed by APDS later.

But there is no accounting for Army and Governmental bureaucracy and infighting..........
 
26 February 1942. Grik, Malaya.
26 February 1942. Grik, Malaya.

Major Tom Craig accepted the cup of strong sweet tea with gratitude. As 7th Bn RTR D Squadron’s Officer Commanding, any kind of fluid replacing all the sweat was a relief. With temperatures above 80° (F) and humidity about 80%, life inside a tank was pretty awful. At least Craig could stick his head outside the turret’s hatch, though the smell of the jungle decay and unburied dead wasn’t much better than the fug from three men in a hot confined space.

His Squadron had made it up the trail to Grik, surprisingly only losing one tank from the ten that had started. Unfortunately, that tank had rolled down a steep embankment, killing two of the crew and severely injuring the others. Once they’d arrived at 53rd Infantry Brigade’s HQ, his nine Matilda IIs had had a few days to get some much-needed maintenance. A and B Squadrons were also present at Grik, and between all three, they had 24 tanks capable of action. The miraculous arrival of a Workshop lorry from one of the Light Aid Detachments had allowed some of the harder jobs to be undertaken, otherwise there would only have been eighteen tanks available.

The infantry of 53rd and 54th Brigades were holding position as the RASC transport attempted to get enough supplies for them to be able to move forward again. The 5th Battalion Norfolk Regiment were furthest forward, pushing patrols forward towards Kroh. So far, they had only been meeting rear-guard actions, so just where exactly the main body of the Japanese army was unknown.

Craig had finished his tea as the meeting with the other Squadron commanders and troop leaders continued to discuss the current situation and figure out their next moves. The good news was that a fresh round of tea was passed to him, and he knew he could savour this one a bit more. The two Brigade Commanders, Cecil Duke (53rd) and Edward Backhouse (54th) were under orders to hold in place until enough supplies were on hand. The senior Quartermasters in both Brigades estimated that it would take another few days before sufficient material was on hand to allow forward movement.

Lieutenant-General Percival had decided to have the Australians move forward to positions around Gurun and to hold there until his successor, Lieutenant-General Alan Cunningham was in place at the beginning of March. 18th Division were to retake Kroh and to establish themselves on the Thai border and protect the Australians’ right flank. When Brigadier Duke had received his orders regarding occupying Kroh and sealing the road from Thailand he requested a Squadron of tanks to support him. Lt-Col Jock Holden (CO 7th Bn RTR) had decided to merge the running tanks into two Squadrons of twelve tanks each. Since D Squadron had nine of the runners, a troop from B Squadron was added to Craig’s command. The rest of A and B Squadrons would merge. Craig’s D Squadron would support Duke’s 53rd Brigade, and A Squadron would support Backhouse’s 54th Brigade.

Once the meeting had broken up, Craig made his way to Duke’s Brigade HQ to sort out the details of what the Infantry CO wanted. Very sensibly (from Craig’s point of view) Duke wanted the twelve tanks to stick together with his Brigade HQ and be allocated to one of the Infantry Battalions as and when required. Craig had worried that the he’d have to allocate one of his troops to each Battalion, so this was a better way of going about things. When Craig requested that each Battalion should have at least a few hours training and familiarisation with his tanks, Brigadier Duke was happy to oblige. During the previous fighting the tanks and the infantry had learned that they needed to work together to defeat the Japanese. Going forward over the terrain towards Kroh would need every bit of that cooperation.

To Craig’s delight the meeting with Brigadier Duke had included another cup of tea, and for the first time in quite a few days Craig felt that his liquid levels were about where they should be. The advantage of tea was that the water had to be well boiled, so avoiding any kind of stomach upset was a bonus.
 
True but the Victor isn't likely to be in full service before 1942. Of course the fact that Vickers delivered the 1931 gun in 3" as well as 75mm begs the question why they couldn't revert to 3" if the Ordnance kick up a fuss.
They could. A difference of 1 mm is kind of a non-issue when it comes to filling a case. As shown by the OTL HV 75 mm which became the 77 mm basically just by switching the 17 pounder projectile into it.

The M48 HE round weighed 14.9 pounds, and had a 1.47 pound charge. The 17-pounder round weighed 15.4 pounds, but onlyy had a 1.28 pound charge.
I’m aware. The 17 pounder HE was meant to withstand a much higher velocity to match the flight path of the AP round more closely. For reference when they were considering the OTL HV 75 mm they downrated the HE shell to 1500 fps (compared to 2650 fps on the AP) because they didn’t think the M48 American HE projectile could take the higher pressure (presumably meaning the HV 75 mm would have have dual sights).

However, this doesn’t really tell me how much is enough. Is the 0.19 lbs (86 g) of extra explosive filling required or would 1.28 lbs be enough for service requirements?

Maybe, but they're going to get a while new tank in probably 1944.
Possibly. And that might be enough for them. But considering they are assuming that the Germans are developing in the same lines as they are do they feel comfortable with the lower penetration when they could get more for a small lose of HE?

To be clear here. I am not against the idea of using the Vickers 75 mm projectile in a HV shell, and though I am a little iffy on using the US shells, they should be alright. I am just not clear on the priority here. HE performance was a priority when you had 2 and 6 pounders without any. Is it such a priority that getting the extra 85 g of it from a U.S. shell is worth the loss of AP performance? I don’t know. I suspect thé OTL British would say no, but I am not sure on TTL’s version.

More options in 75mm. A better HE round, a canister round, a white phosphorous (presumably an incendiary) round, etc. They don't need an exception AP round just yet, since Panthers won't show up until 1943.

Were any of those used in British 75 mm guns OTL?

Sherman 75mm base model will be a great advantage logistically.
On this I am not so sure. The documents that discuss the OTL HV 75 mm make it clear there was no production of this caliber in the UK when they were discussing it (spring 1943). Setting some up was being considered but it did not exist at that point and in the event May never have done. Which means that your supply line for this ammunition stretches across the Atlantic. And while that is probably doable ( they managed on the 75 mm in British service IOTL) I am not sure that it was an advantage.

However, since we are effectively retreading the same ground that we have covered before, I should probably shut up and stop cluttering up the thread.
 
The M48 HE round weighed 14.9 pounds, and had a 1.47 pound charge. The 17-pounder round weighed 15.4 pounds, but onlyy had a 1.28 pound charge.
That's part of the story, the M48's 667g worth of HE filling is about equaled by the 17pr high capacity shell at 645g, and dwarfed by the 17pr super high capacity at 875g.
 
I would point out that in HE rounds it's usually the fragmentation rather than the blast itself which is most lethal. The HE charge is there not only for blast/cover destruction but most importantly to make and propel high energy fragments. As such a small difference in payload doesn't necessarily translate to a significant difference in lethality.
 
They could. A difference of 1 mm is kind of a non-issue when it comes to filling a case. As shown by the OTL HV 75 mm which became the 77 mm basically just by switching the 17 pounder projectile into it.


I’m aware. The 17 pounder HE was meant to withstand a much higher velocity to match the flight path of the AP round more closely. For reference when they were considering the OTL HV 75 mm they downrated the HE shell to 1500 fps (compared to 2650 fps on the AP) because they didn’t think the M48 American HE projectile could take the higher pressure (presumably meaning the HV 75 mm would have have dual sights).

However, this doesn’t really tell me how much is enough. Is the 0.19 lbs (86 g) of extra explosive filling required or would 1.28 lbs be enough for service requirements?


Possibly. And that might be enough for them. But considering they are assuming that the Germans are developing in the same lines as they are do they feel comfortable with the lower penetration when they could get more for a small lose of HE?

To be clear here. I am not against the idea of using the Vickers 75 mm projectile in a HV shell, and though I am a little iffy on using the US shells, they should be alright. I am just not clear on the priority here. HE performance was a priority when you had 2 and 6 pounders without any. Is it such a priority that getting the extra 85 g of it from a U.S. shell is worth the loss of AP performance? I don’t know. I suspect thé OTL British would say no, but I am not sure on TTL’s version.



Were any of those used in British 75 mm guns OTL?


On this I am not so sure. The documents that discuss the OTL HV 75 mm make it clear there was no production of this caliber in the UK when they were discussing it (spring 1943). Setting some up was being considered but it did not exist at that point and in the event May never have done. Which means that your supply line for this ammunition stretches across the Atlantic. And while that is probably doable ( they managed on the 75 mm in British service IOTL) I am not sure that it was an advantage.

However, since we are effectively retreading the same ground that we have covered before, I should probably shut up and stop cluttering up the thread.

I really enjoy the little details so every note, thought and clarification is always appreciated.... 🍻
 
We finally know what determined the strength of nations. Japan started the war with superiority in tea, but the British Empire soon caught up with them and is now clearly gaining an edge, especially thanks to tea with milk.
 
On the subject of gun calibre I think an improved longer (70 cal?) 75mm firing a higher velocity round coupled with early sabot rounds and reduced charge HE should see out British tank armament for WW2 especially as the designs rapidly evolve into universal tanks.

An analogous long (otl it was a 66 cal) 20 pounder / 84mm should serve end of war designs but the above improved 75mm gun should deal with pretty much anything.

Perhaps a 20 pounder could retrofit into TD designs with TTLs end of war Centurion starting with this gun (perhaps initially due to super panzer scare the price to be groundless / and IS3?)

Larger calibre guns mean larger ammo and larger tanks.
 
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