Yes, but people reading this TL on this blog weren't the people taking the decisions in 1941-3. So our views are not really a guide to sound policy then.
Sir John Valentine Carden survives.
- Thread starter allanpcameron
- Start date
- Status
13 November 1940. London, England.
allanpcameron
Donor
13 November 1940. London, England.
Since both the Vickers A23 Victor and Vauxhall’s A22 design would have 4 inches of armour, and having been informed by intelligence sources that 4 to 6 inches of armour might, likewise, appear on German tanks, Major-General Campbell Clarke, as Director of Artillery, had had to do something. The 6-pdr gun, not yet in mass production, hadn’t been designed to deal with 100mm of armour at any reasonable range. A new anti-tank gun would be needed to replace the 6-pdr, and so he’d sent a request the previous month to various design teams to invite them to think about solutions.
It seemed horribly inevitable that the Vickers gun design team had answered already. As part of the design work for the A23 Victor, they had done a lot of work on a 3-inch gun derived from their Model 1931 75mm anti-aircraft gun. They had chosen to use the Finish version of the gun, which used 76.2mm x 505R shells. The work they had done on the pilot model had given them solid evidence that, with the right kind of armour piercing shell this would provide the capability to deal with 4-inches of armour at a decent range. They also had shown that their new 3-inch gun would be able to fire a good sized HE and smoke shell.
The problem that Clark, and the Ordnance Department, had with this idea was that there was no history of producing shells in the Finnish size. The only British 3-inch shells currently being produced were the 76.2mm x 420R for the old 3-inch 20 cwt AA gun and the 76.2mm x 134R for the new Close Support tank howitzer. The 14lb shell Vickers were thinking about would be a problem when there were limited resources for making shells and filling them. He wrote to them telling they would need to consider the 7.62mm x 420R, which would probably better suit a tank gun anyway. A 12.5lb AP shell should provide adequate penetration, and still be suitable for the HE role. He went on to suggest that the gun design team look at the 3-inch 20 cwt AA gun, which in his opinion would outperform the Model 1931 75mm gun as a basis for a large high velocity gun.
When Clarke had looked at the gun data, he wasn’t overly impressed. Vickers stated that the gun’s muzzle velocity was 2500ft per second. It seemed to Clarke that they were more concerned about having a dual-purpose tank gun rather than being able to destroy enemy tanks, which was still the primary role of the tank gun. What the Vickers report did do was it made him think that a 3-inch gun was a good place to start to look at for the calibre needed to provide a dedicated anti-tank gun, which would need to be something nearer 3000ft per second to deal with 4-5 inches of armour. Doing some rough sums, it would need a shell around 17 pounds to provide the kind of penetration required. It would be interesting to see what the team at Woolwich Arsenal would come up with, but it would certainly be better than the Vickers gun.
When he’d been told that Vauxhall were designing the A22 for the 2-pdr, he’d warned his boss (Director General of Munitions Production Sir Harold Brown) that this was short-sighted. The design, approved by Major-General Alexander Davidson the Director of Mechanisation, had gone with the new 3-inch tank howitzer in the hull and a turret with the 2-pdr. Clarke believed that the 6-pdr would be the least a tank would need. Just as the British had studied the captured German equipment, there was no doubt that the 2-pdr and the Matilda were undergoing a similar examination. The fact would be that the Germans would increase their gun and their armour, and both the new tanks being brought into production were still armed with only the 2-pdr.
If Vickers were already thinking about a 3-inch gun for the A23 Victor, and even if their initial order started with the 6-pdr, as Clarke had requested, until their 3-inch gun was mature enough, it could well be ready around the same time as the A22. It would make the A22 look almost toothless in comparison. The exact same thing could be said for the Nuffield A15. He called in his secretary and dictated a memo to Davidson requesting that both the A22 and A15 should be looked at again to see if they could be adapted to fit the 6-pdr. He conceded it may have to wait for the initial order to be completed with the 2-pdr as the 6-pdr still wasn’t in mass production. But he argued strongly that both tanks should be readied for a bigger gun as soon as possible.
As a piece of mental gymnastics, he tried to envision what would come after, a gun capable of taking on 7 to 8 inches of armour. The 3.7-inch AA gun gave him a starting point, with roughly the same muzzle velocity it would need a shell of around 32 pounds to penetrate at any decent range. Beyond that, they’d probably need to talk to the Royal Navy about borrowing a battleship.
Leaving aside the Vickers report, the next report on his desk was the results of the final tests on the captured German tank ammunition. There were a number of interesting, and frightening, things that the 37mm German Panzergranate 39 armour piercing shell had shown up. The obvious thing was that it had both a penetrator cap and a ballistic cap. The only reason for the penetrator would be to deal with face-hardened armour, and certainly there was a bit of that on the captured Panzer IV. It might also explain why some of the German hits on British tanks had failed to penetrate the armour, as British tanks didn’t use face-hardened armour. If that was the expectation that the Germans were working on, then it could be deduced that this was probably the way the Germans were going themselves. If the German tanks were moving to face-hardened armour then the current un-capped 2-pdr shells would need to be looked at, as would the new 6-pdr.
The notion of a ballistic cap to improve aerodynamics wasn’t unheard of, but this was the first time that Clarke had seen it used, and used effectively, on a tank shell like the 37mm on the captured Panzer III. It was certainly something that had got the boffins at Woolwich interested. Among the reports recommendations was that a number of shells for the 2-pdr and 6-pdr should be modified as Amoured Piercing Capped Ballistic Cap (APCBC) and fully tested.
The other armour piercing shell tested was for the Panzer IV’s short 75mm/L24 cannon was the “Panzer Kannon Grenade with red band” (K.Gr rot Pz.). That shell had been found to have a large cavity for an explosive charge of 80 grams. When tested it showed that when it penetrated a tank it caused a disastrous burst effect inside the tank. The 2-pdr APHE shell was designed to do the same thing, but obviously with a far smaller explosive charge. With the bottleneck in producing 2-pdr shells this had been dropped to concentrate on the solid shot. As an idea, it was certainly worth exploring. Much of the work on the 6-pdr shells had already been done, but with the tank branch looking to use it on the Mark II Valiant, they were already asking for an HE shell, and having an improved APHE would probably be appreciated too. Clarke signed off on the recommendations and glanced at the clock to see how much more work he could get done before the typists in the pool left.
NB text in italic differs from OTL. The birth of the 17-pdr is as noted here. I am no weapons expert and don't want to pretend to be one. I've taken what info I can find on the various guns and gone with that info. So people who are experts feel free to pick the thing to pieces. Everyday is a school day. Happy to be corrected if I'm wrong about stuff. The conflict between Clarke as Director of Artillery and Vickers is OTL. I believe it may be because he wants to protect his own design team's work at Woolwich to which Vickers is the only British alternative. He did make the case for 6-pdrs in A22 and A15 at about this time.
Capturing the German tanks was a deliberate ploy on my part. It allows the work that is only done much later in the Middle East on captured German equipment can be done before they encounter the Pz III and IV with doubled and face hardened armour. The thicker armour on the Valiants should help against the 50mm gun they've gone to too. The 2-pdr in mid-late 1941 with an APC shell, will help. A 6-pdr in mid-late 1941 with APCBC, HE and APHE, well that's just the gravy.
Since both the Vickers A23 Victor and Vauxhall’s A22 design would have 4 inches of armour, and having been informed by intelligence sources that 4 to 6 inches of armour might, likewise, appear on German tanks, Major-General Campbell Clarke, as Director of Artillery, had had to do something. The 6-pdr gun, not yet in mass production, hadn’t been designed to deal with 100mm of armour at any reasonable range. A new anti-tank gun would be needed to replace the 6-pdr, and so he’d sent a request the previous month to various design teams to invite them to think about solutions.
It seemed horribly inevitable that the Vickers gun design team had answered already. As part of the design work for the A23 Victor, they had done a lot of work on a 3-inch gun derived from their Model 1931 75mm anti-aircraft gun. They had chosen to use the Finish version of the gun, which used 76.2mm x 505R shells. The work they had done on the pilot model had given them solid evidence that, with the right kind of armour piercing shell this would provide the capability to deal with 4-inches of armour at a decent range. They also had shown that their new 3-inch gun would be able to fire a good sized HE and smoke shell.
The problem that Clark, and the Ordnance Department, had with this idea was that there was no history of producing shells in the Finnish size. The only British 3-inch shells currently being produced were the 76.2mm x 420R for the old 3-inch 20 cwt AA gun and the 76.2mm x 134R for the new Close Support tank howitzer. The 14lb shell Vickers were thinking about would be a problem when there were limited resources for making shells and filling them. He wrote to them telling they would need to consider the 7.62mm x 420R, which would probably better suit a tank gun anyway. A 12.5lb AP shell should provide adequate penetration, and still be suitable for the HE role. He went on to suggest that the gun design team look at the 3-inch 20 cwt AA gun, which in his opinion would outperform the Model 1931 75mm gun as a basis for a large high velocity gun.
When Clarke had looked at the gun data, he wasn’t overly impressed. Vickers stated that the gun’s muzzle velocity was 2500ft per second. It seemed to Clarke that they were more concerned about having a dual-purpose tank gun rather than being able to destroy enemy tanks, which was still the primary role of the tank gun. What the Vickers report did do was it made him think that a 3-inch gun was a good place to start to look at for the calibre needed to provide a dedicated anti-tank gun, which would need to be something nearer 3000ft per second to deal with 4-5 inches of armour. Doing some rough sums, it would need a shell around 17 pounds to provide the kind of penetration required. It would be interesting to see what the team at Woolwich Arsenal would come up with, but it would certainly be better than the Vickers gun.
When he’d been told that Vauxhall were designing the A22 for the 2-pdr, he’d warned his boss (Director General of Munitions Production Sir Harold Brown) that this was short-sighted. The design, approved by Major-General Alexander Davidson the Director of Mechanisation, had gone with the new 3-inch tank howitzer in the hull and a turret with the 2-pdr. Clarke believed that the 6-pdr would be the least a tank would need. Just as the British had studied the captured German equipment, there was no doubt that the 2-pdr and the Matilda were undergoing a similar examination. The fact would be that the Germans would increase their gun and their armour, and both the new tanks being brought into production were still armed with only the 2-pdr.
If Vickers were already thinking about a 3-inch gun for the A23 Victor, and even if their initial order started with the 6-pdr, as Clarke had requested, until their 3-inch gun was mature enough, it could well be ready around the same time as the A22. It would make the A22 look almost toothless in comparison. The exact same thing could be said for the Nuffield A15. He called in his secretary and dictated a memo to Davidson requesting that both the A22 and A15 should be looked at again to see if they could be adapted to fit the 6-pdr. He conceded it may have to wait for the initial order to be completed with the 2-pdr as the 6-pdr still wasn’t in mass production. But he argued strongly that both tanks should be readied for a bigger gun as soon as possible.
As a piece of mental gymnastics, he tried to envision what would come after, a gun capable of taking on 7 to 8 inches of armour. The 3.7-inch AA gun gave him a starting point, with roughly the same muzzle velocity it would need a shell of around 32 pounds to penetrate at any decent range. Beyond that, they’d probably need to talk to the Royal Navy about borrowing a battleship.
Leaving aside the Vickers report, the next report on his desk was the results of the final tests on the captured German tank ammunition. There were a number of interesting, and frightening, things that the 37mm German Panzergranate 39 armour piercing shell had shown up. The obvious thing was that it had both a penetrator cap and a ballistic cap. The only reason for the penetrator would be to deal with face-hardened armour, and certainly there was a bit of that on the captured Panzer IV. It might also explain why some of the German hits on British tanks had failed to penetrate the armour, as British tanks didn’t use face-hardened armour. If that was the expectation that the Germans were working on, then it could be deduced that this was probably the way the Germans were going themselves. If the German tanks were moving to face-hardened armour then the current un-capped 2-pdr shells would need to be looked at, as would the new 6-pdr.
The notion of a ballistic cap to improve aerodynamics wasn’t unheard of, but this was the first time that Clarke had seen it used, and used effectively, on a tank shell like the 37mm on the captured Panzer III. It was certainly something that had got the boffins at Woolwich interested. Among the reports recommendations was that a number of shells for the 2-pdr and 6-pdr should be modified as Amoured Piercing Capped Ballistic Cap (APCBC) and fully tested.
The other armour piercing shell tested was for the Panzer IV’s short 75mm/L24 cannon was the “Panzer Kannon Grenade with red band” (K.Gr rot Pz.). That shell had been found to have a large cavity for an explosive charge of 80 grams. When tested it showed that when it penetrated a tank it caused a disastrous burst effect inside the tank. The 2-pdr APHE shell was designed to do the same thing, but obviously with a far smaller explosive charge. With the bottleneck in producing 2-pdr shells this had been dropped to concentrate on the solid shot. As an idea, it was certainly worth exploring. Much of the work on the 6-pdr shells had already been done, but with the tank branch looking to use it on the Mark II Valiant, they were already asking for an HE shell, and having an improved APHE would probably be appreciated too. Clarke signed off on the recommendations and glanced at the clock to see how much more work he could get done before the typists in the pool left.
NB text in italic differs from OTL. The birth of the 17-pdr is as noted here. I am no weapons expert and don't want to pretend to be one. I've taken what info I can find on the various guns and gone with that info. So people who are experts feel free to pick the thing to pieces. Everyday is a school day. Happy to be corrected if I'm wrong about stuff. The conflict between Clarke as Director of Artillery and Vickers is OTL. I believe it may be because he wants to protect his own design team's work at Woolwich to which Vickers is the only British alternative. He did make the case for 6-pdrs in A22 and A15 at about this time.
Capturing the German tanks was a deliberate ploy on my part. It allows the work that is only done much later in the Middle East on captured German equipment can be done before they encounter the Pz III and IV with doubled and face hardened armour. The thicker armour on the Valiants should help against the 50mm gun they've gone to too. The 2-pdr in mid-late 1941 with an APC shell, will help. A 6-pdr in mid-late 1941 with APCBC, HE and APHE, well that's just the gravy.
Last edited:
I think it was in this thread that we earlier had a fun discussion on what should arm a British Ratte. I am not saying this was a good or serious idea (it wasn't), but the thought of something the size of a destroyer with a single battleship size gun in a comically large turret rolling across the North German plain does make me chuckle.
Beyond the fact that 32pdr was not the first weight of shot considered for a 3.7" AT gun at the time (there was 28, 30 and 37 before), nothing wrong. I reckon APHE still won't make a comeback as it had somewhat poorer armor penetration and was not deemed worth it by most Allied countries.
Actually it still gets a lot of ice, but not enough to close it.
Derek Pullem
Donor
APHE in a 6pdr would be lethal against early Panzer III and IV. Later it would be much less effective.
Most Northern Russian ports out from the Baltic suck to try and navigate into Even at the best of times.
allanpcameron
Donor
I came across this quote from here, which was why I mentioned it. I may also have read somewhere it was French 75mm ammo captured in Syria that was converted to use in US 75mm guns. Again, NB, in the update, Clarke is signing off on testing, not production.
Nice update, I do feel like I am banging on about this gun though so sorry. I also don't claim to be an expert, just an amateur with an interest and access to the internet.
On the Finnish M1931 Vickers AA gun. I am sure they used the 605mmR shell from the Bofors Model 1928 AA gun. That gun was the standard Finnish AA gun as far as I am aware and came in two versions, the 7.5cm with a 605mmR case and an 8cm version with the 505mmR case. I think the 8cm was a special calibre for Hungary or somewhere near there so I cant see the Finns using that, plus they were one of the first adopters when the gun was only a 75mm I think. Also checking here has the Finns using the 76.2x605R and if I trust Anthony Williams on anything it is cartridges, look at the second red entry.
Now if I am right that gun fired a 14pound shell at 2800ft/s, not too shabby at all, particularly given that was with, I would assume, mid 1920's propellants at best. Also it is probably a bit long to fit in a tank given it was only being looked at mid 39 to begin with. Now what could that mean, well the 3" 20cwt was a Vickers design wasn't it or at least a modification of one so Vickers would likely have the equipment and specs of not only the 3" 20cwt but more importantly the 420mm shell. I do think using the M1931 as the basis of the tank gun is still correct though given it is newer and lighter.
Britain used, by 1939, basically 2 shell weights in the 3" calibre as you note in the post, 12.5 pounds and 16 pounds. And whilst I am pretty sure the Finnish order used the 14 pound shell of the 7.5cm M28 Bofors (another reason I think they used the longer case) I don't think Vickers or anyone in Britain actually manufactured that ammo. Given that I would have expected Vickers to, rather than design a new shell, adapt an existing one and that would likely be the 16 pound shell given the requirement for good HE performance.
TL;DR on all that.
I think the Finns used the bigger 605mm cartridge case. Vickers would have had ample access to the 420mm 3"20cwt case so would likely have used that if true. The M1931 is a better starting point than the rest of the 3" 20cwt. If looking to use a shell of 3" already in production then the 16 pound shell of the 20cwt would be the likely bet.
Now If I am right on that what that means for the 17 pounder I will leave up to you/others until more concrete posts have been made.
As for the 32pdr as @Bougnas points out 32 pounds was a pretty late decision on projectile weight. I also thought it wasn't really looked at until 1942 at the earliest.
Some other notes Vickers did use a 14.5 pound shell in a 495mm case for the M1931 in 75mm. Thing is, particularly given the starting point of 1939 I cant see Vickers going for a case that long even to put in a tank.
Helpful?
Last edited:
Considering that the 3" 20cwt was only used in a very small scale basis in the Churchill Gun Carrier and Vickers designed a brand new gun to use the gun's cartridge for the 75 HV (and 77), I guess that the 3" 20cwt's design was not only obsolete but was not thought to be any quicker to re-enter production than a new gun. Therefore considering that Vickers has only worked on the M1931 so far it would make sense to keep the gun's design but adapt it to the 3" 20cwt cartridge if needed, or even the M1931 75mm case necked out for a 3" projectile as it would be a good middle ground.
IMO the 420mm case length of the 3" 20cwt would be the most logical and likely choice as 605mm is simply too long in WW2 for such a "weak" gun in a tank. The 105mm L7's was 615mm long but for an incomparably stronger gun. Now I don't have a picture of the Swedish round for reference but it should be possible to keep the same case volume in a shorter package by using a stubby cartridge like the 17pdr, as long as the neck is not too serious. However I don't think it is worth taking this much effort and I think that a slightly modified 3" 20cwt cartridge should be more than enough as shown by the 75 and 77 HV guns OTL.
If I recall, with the new projectile made for it the Churchill GC's 3" was pretty decent even with a rather short barrel.
In any case, even if the 3" in the Victor turns out to be weaker than the 75 or 77HV, as long as it's better than the 75mm M3 it is still excellent for 1942.
marathag
Banned
So were US GMC trucks, at least they had a M2
.50 to defend themselves.
Both were logistics items.
So Vickers choosing the M1931 as a basis for the gun is the right move for multiple reasons, I don't think that can be argued. The cartridge and case length chosen can be though. I think another reason to use the 420mm case would be availability. The 3" 20cwt is still in service and I would assume ammunition is still being made. Given that it would be far easier to take that already in use and production case and adapt it to tank use than either design something new or take something not actually being made in Britain and start making it.
If the 605mm was used it would be a pretty powerful gun, 14 pounds at 2800 ft/s in 1928 is pretty impressive. Using more modern propellants for instance could really boost performance. Fitting the gun and the ammo into a tank in 1939 however would seem like a massive task.
One other candidate for a big gun could be the 4" AA gun in service with the RN. Not too long a round, fairy high MV, and readily available
A 4" projectile in a tank would probably be too much right now at the muzzle velocities required. Using the 4" Mk IV, XII, XIX case as a necked down to 3" might have been a decent idea though. 504/533mmR and 133 mm case diameter. That's slightly thinner than the 155mm diameter of the 17pdr whilst being a bit shorter.
Last edited:
Shooting down He 111's with a tank is a bit much wouldn't you say.But they could use them to shoot down aircraft as well!
- Status