There is always the Vickers 24.5mm Auto cannon, mount one of those in turret/tank of your choice and it chew any Italian tank to rusty shreds. I alsys thought that this would make a very good gun for a WW2 armoured car.
The Forge of Weyland
- Thread starter Astrodragon
- Start date
marathag
Banned
Not so much as it was needed against the Tankette, as just what the top limit would be for that size turret ring.
That said, yeah, the 47mm is overkill.
But then, there is no kill like overkill
Vickers Mk VIB with a 2pd-47mm class gun would make for a nice SPG, in a way.
Mobile, and immune from MG fire
That would be good for setting up an ambush. Fire 2 or 3 rounds at approaching enemy armour, then disappear quick to a fall back position before the enemy can target you. The turret needs a top to it though!
This picture is of a German SPG conversion of the Vickers Mk VI. This shows that a reasonable size support weapon was possible using the Vickers MkVI as a base vehicle
The picture below shows a MkVI converted to a prime mover/load carrier by the Germans and gives a further indication of the possibilities of development open to Carden.
This third German version is a dedicated ammunition carrier.
So a complete light armoured family is practical. It may be a bit on the light side but is based on current production.
some of the neccesary conversions could done using older marks of the light tank that are now basically obsolete.
The picture below shows a MkVI converted to a prime mover/load carrier by the Germans and gives a further indication of the possibilities of development open to Carden.
This third German version is a dedicated ammunition carrier.
So a complete light armoured family is practical. It may be a bit on the light side but is based on current production.
some of the neccesary conversions could done using older marks of the light tank that are now basically obsolete.
January Vickers meeting, part 1
January 1936, Vickers Engineering. (part 1)
With the way international relations seemed to be deteriorating, and the consequent possibilities for Vickers in arms sales, a number of meetings of the various areas of responsibility had been arranged for the start of the year. The one that most concerned Sir John Carden was the armoured vehicle meeting.
He'd been giving considerable thought to the problems of meeting the specifications the Army had been coming up with, the main problem being that the army had unreasonable ideas about just what could be built within the weight limits they specified. He'd decided that he was going to use the license they'd agreed to on his designing the new Cruiser and infantry tank to show them what they needed to do the jobs they asked for, rather than let them just waste time trying to squeeze a quart into a pint pot. Hopefully they would agree to adjust the requirement to something more believable.
The first item up for discussion was the request from the Army to look into putting a cannon of some sort on the MkVI light tank. This was seen as actually fairly easy; a version of their light tank had been sold to Latvia with such a cannon, and the Russian T-26 was a turreted light tank based on their original design. The Latvian order was due to be delivered next year, and they hadn't actually built any yet, but the design of the turret was done and in fact they'd built a wooden mock-up to check everything would fit. So it was really just a matter of working out the maximum size gun that would fit, then seeing what the Army wanted that would fall inside that parameter. The light tank was pretty easy to produce, and some of Vickers associate firms could build them as well as Vickers themselves. Whether such a tank was any use of not, a number of the experts had disputed, but giving the Army a cost for them probably wouldn't hurt.
Given the limited size, and the fact they wanted an urgent fix, gun discussion had centred on models already available. This had come down to three possibilities. First, the current low velocity 3pdr. As this was the current fitting for the medium tanks, some spares were available, and the production line was still active. Second was the new 2pdr gun. This was a better anti-tank gun, but they weren't sure if the army would be happy to have the initial production diverted, which is what would be needed. The third option was the COW gun. While lighter than the other two, and with inferior penetration, it was still more than capable of killing a tankette. While this gun wasn't being used by the army, they had a few models available, and the production line could be re-opened. The gun was clip fed, which might be a useful addition allowing a burst of rounds against an evading target. One advantage of this gun was the engineers could fit it in place of the 0.5" machinegun, although this would make the turret cramped. Realistically the slowest part of any modification would be the turret, so whichever gun was chosen availability wouldn't be an issue.
The other decision they needed the army to make was if they wanted to convert existing models, or build new. 22 of the Mk V were being built, and they would soon be delivering the Mk VI - orders for 51 of this tank had already been placed. They could modify existing Mk V's, although the Army weren't plentifully supplied. One other possibility that had been raised was a version of the 6-tone Vickers tank. This had been made in a version with a turret, and successfully sold abroad, although the British Army hadn't bought any. They still had the plans, and if new build tanks were required they could offer this as an alternative.
Once the easy questions had been got out of the way, discussion turned to a more contentious topic - the proposed Cruiser and Infantry tanks. Sir John and his team had been looking seriously at these for some months, starting from the A9 and A10 designs, neither of which would fill the new requirements.
The initial and biggest problem was the engine needed. The current bus engines weren't up to driving even the cruiser tank at anything like the speed required, and the heavy infantry tank was even worse. The problem was that the Army was quite keen on some designs soon, so a long wait would be unacceptable if they suggested a custom-built engine. Given the small numbers the Army tended to order in, this would likely be too expensive anyway.
So Sir John and his team had started to look around, and hold conversations with various people about what engines were actually available, or could be modified or put into production at a relatively low cost. Based on the weights expected and the performance the Army wanted, Sir John had estimated they would need something delivering 300 - 400hp. A diesel might be a better option, assuming they had a choice, as it would power a tank more efficiently and me more economical on fuel. A big engine would require a correspondingly large fuel tank.
The first option was to use two of the existing bus engines together. None of the engineers really liked the idea. Yes, two coupled diesel engines would give somewhere around 350hp, depending on which engines they started with. But there was the issue of the cost and complexity of all the mechanicals necessary to do that coupling, the loss of efficiency, and the high maintenance cost. Such a solution was considered to be a fallback one if they couldn't find a more suitable one.
The engines that did produce the sort of power output they needed were normally aircraft engines or marine diesels. Aircraft engines, while light and usually small, were expensive, and rather fragile by tank standards. Marine engines were robust, but heavy and often large, things that were of less importance in a ship that in a tank.
Sir John had had some interesting conversations with his friend Harry Ricardo. He'd designed the diesels used in the WW1 tanks, as well as pioneering many modern diesel developments, and he'd wanted to get his input. He knew that Ricardo had modified one of Rolls-Royces Kestrel aero engines to run as a diesel for the 'Flying Spray' car, which was soon to make an effort at some land speed records. He was particularly interested in this as the car and engine had been designed for endurance records rather than pure short-term speed, so would be more likely to stand up to use in a tank. Ricardo had modified an old Kestrel Rolls-Royce had let him have, reducing the capacity and adding sleeve valves while turning it into a diesel. Ricardo told him that yes, he saw no reason why the engine shouldn't work as a tank engine. With the modifications he'd made, the output had been reduced from around 500 to 340hp, but he felt that while the un-supercharged petrol version would in theory get close to 500hp, there would be big issues with the low-quality pool petrol used in the Army. Part of the reduction in performance had been caused by the reduction in the valve bore size to allow for the insertion of a sleeve valve. If a little more power was needed, he thought it would be possible to increase the bore a little to retain the old volume even with a sleeve valve, which would give around 380hp, although this would mean new machinery to make the engine. The aero engine wasn't cheap, a standard Kestrel was about £2,000, but he felt that but leaving off all the unneeded parts, and possible replace some parts with lower cost, heavier alternatives would allow this to be reduced. The problem was production. Rolls-Royce was very busy with the production of their aero engines, and realistically a new production line would have to be set up, perhaps elsewhere with Rolls-Royces cooperation.
The next engine to be looked at had been the engine used in one of the Medium Mk III prototypes. Initially a 180hp engine had been fitted, but this had shown to be underpowered, and in the third prototype a Thornycroft 6V 500 hp, a slow revving marine engine had been fitted. This would certainly provide the power necessary, maybe even more than necessary, although the engine was rather heavy. It was noted that it would be worthwhile to see if the weight and cost could be reduced even if this reduced the power. Even with a reduction in power, this engine was a good candidate for the heavy infantry tank.
The final promising engine was a version of the Paxman R-series marine diesel. Ricardo had mentioned this to him, as the way they were built allowed customisation of the number of cylinders. They had a number of advantages; they were built in a robust form (they supplied a version for the Navy to use in Submarines) that were resistant to shock, which would be a valuable trait for a tank engine. They could be produced to give around 500hp. The main issues would be weight and cost. Ricardo was very familiar with the design - they used the Comet head he'd designed in some of their engines- and he pointed out that setting up for a series production run would likely reduce the costs considerably.
While there were obvious problems with all the likely candidates, the problem now looked solvable. A decision was taken to investigate the three promising candidates more fully, and costs estimated for a run of either 250 or 500 engines. Even if the Army didn't want them all, the foreign market would likely be interested in more powerful tanks, and if not they could sell them for marine use. This was to be done as soon as possible so a decision could be made on usage. For his part, Sir John liked the look of the diesel Kestrel, if production could be arranged. Given its origin of Rolls-Royce and Ricardo, he felt reliability, a constant problem with high powered engines, wouldn't be an issue. 340hp should drive his idea of a Cruiser tank nicely, and one of the higher power engines would be a good fit for his Infantry tank idea. Given the much heavier weight the infantry tank was likely to be, he was starting to think that a common engine, while good for production, wouldn't be the best technical solution.
With the way international relations seemed to be deteriorating, and the consequent possibilities for Vickers in arms sales, a number of meetings of the various areas of responsibility had been arranged for the start of the year. The one that most concerned Sir John Carden was the armoured vehicle meeting.
He'd been giving considerable thought to the problems of meeting the specifications the Army had been coming up with, the main problem being that the army had unreasonable ideas about just what could be built within the weight limits they specified. He'd decided that he was going to use the license they'd agreed to on his designing the new Cruiser and infantry tank to show them what they needed to do the jobs they asked for, rather than let them just waste time trying to squeeze a quart into a pint pot. Hopefully they would agree to adjust the requirement to something more believable.
The first item up for discussion was the request from the Army to look into putting a cannon of some sort on the MkVI light tank. This was seen as actually fairly easy; a version of their light tank had been sold to Latvia with such a cannon, and the Russian T-26 was a turreted light tank based on their original design. The Latvian order was due to be delivered next year, and they hadn't actually built any yet, but the design of the turret was done and in fact they'd built a wooden mock-up to check everything would fit. So it was really just a matter of working out the maximum size gun that would fit, then seeing what the Army wanted that would fall inside that parameter. The light tank was pretty easy to produce, and some of Vickers associate firms could build them as well as Vickers themselves. Whether such a tank was any use of not, a number of the experts had disputed, but giving the Army a cost for them probably wouldn't hurt.
Given the limited size, and the fact they wanted an urgent fix, gun discussion had centred on models already available. This had come down to three possibilities. First, the current low velocity 3pdr. As this was the current fitting for the medium tanks, some spares were available, and the production line was still active. Second was the new 2pdr gun. This was a better anti-tank gun, but they weren't sure if the army would be happy to have the initial production diverted, which is what would be needed. The third option was the COW gun. While lighter than the other two, and with inferior penetration, it was still more than capable of killing a tankette. While this gun wasn't being used by the army, they had a few models available, and the production line could be re-opened. The gun was clip fed, which might be a useful addition allowing a burst of rounds against an evading target. One advantage of this gun was the engineers could fit it in place of the 0.5" machinegun, although this would make the turret cramped. Realistically the slowest part of any modification would be the turret, so whichever gun was chosen availability wouldn't be an issue.
The other decision they needed the army to make was if they wanted to convert existing models, or build new. 22 of the Mk V were being built, and they would soon be delivering the Mk VI - orders for 51 of this tank had already been placed. They could modify existing Mk V's, although the Army weren't plentifully supplied. One other possibility that had been raised was a version of the 6-tone Vickers tank. This had been made in a version with a turret, and successfully sold abroad, although the British Army hadn't bought any. They still had the plans, and if new build tanks were required they could offer this as an alternative.
Once the easy questions had been got out of the way, discussion turned to a more contentious topic - the proposed Cruiser and Infantry tanks. Sir John and his team had been looking seriously at these for some months, starting from the A9 and A10 designs, neither of which would fill the new requirements.
The initial and biggest problem was the engine needed. The current bus engines weren't up to driving even the cruiser tank at anything like the speed required, and the heavy infantry tank was even worse. The problem was that the Army was quite keen on some designs soon, so a long wait would be unacceptable if they suggested a custom-built engine. Given the small numbers the Army tended to order in, this would likely be too expensive anyway.
So Sir John and his team had started to look around, and hold conversations with various people about what engines were actually available, or could be modified or put into production at a relatively low cost. Based on the weights expected and the performance the Army wanted, Sir John had estimated they would need something delivering 300 - 400hp. A diesel might be a better option, assuming they had a choice, as it would power a tank more efficiently and me more economical on fuel. A big engine would require a correspondingly large fuel tank.
The first option was to use two of the existing bus engines together. None of the engineers really liked the idea. Yes, two coupled diesel engines would give somewhere around 350hp, depending on which engines they started with. But there was the issue of the cost and complexity of all the mechanicals necessary to do that coupling, the loss of efficiency, and the high maintenance cost. Such a solution was considered to be a fallback one if they couldn't find a more suitable one.
The engines that did produce the sort of power output they needed were normally aircraft engines or marine diesels. Aircraft engines, while light and usually small, were expensive, and rather fragile by tank standards. Marine engines were robust, but heavy and often large, things that were of less importance in a ship that in a tank.
Sir John had had some interesting conversations with his friend Harry Ricardo. He'd designed the diesels used in the WW1 tanks, as well as pioneering many modern diesel developments, and he'd wanted to get his input. He knew that Ricardo had modified one of Rolls-Royces Kestrel aero engines to run as a diesel for the 'Flying Spray' car, which was soon to make an effort at some land speed records. He was particularly interested in this as the car and engine had been designed for endurance records rather than pure short-term speed, so would be more likely to stand up to use in a tank. Ricardo had modified an old Kestrel Rolls-Royce had let him have, reducing the capacity and adding sleeve valves while turning it into a diesel. Ricardo told him that yes, he saw no reason why the engine shouldn't work as a tank engine. With the modifications he'd made, the output had been reduced from around 500 to 340hp, but he felt that while the un-supercharged petrol version would in theory get close to 500hp, there would be big issues with the low-quality pool petrol used in the Army. Part of the reduction in performance had been caused by the reduction in the valve bore size to allow for the insertion of a sleeve valve. If a little more power was needed, he thought it would be possible to increase the bore a little to retain the old volume even with a sleeve valve, which would give around 380hp, although this would mean new machinery to make the engine. The aero engine wasn't cheap, a standard Kestrel was about £2,000, but he felt that but leaving off all the unneeded parts, and possible replace some parts with lower cost, heavier alternatives would allow this to be reduced. The problem was production. Rolls-Royce was very busy with the production of their aero engines, and realistically a new production line would have to be set up, perhaps elsewhere with Rolls-Royces cooperation.
The next engine to be looked at had been the engine used in one of the Medium Mk III prototypes. Initially a 180hp engine had been fitted, but this had shown to be underpowered, and in the third prototype a Thornycroft 6V 500 hp, a slow revving marine engine had been fitted. This would certainly provide the power necessary, maybe even more than necessary, although the engine was rather heavy. It was noted that it would be worthwhile to see if the weight and cost could be reduced even if this reduced the power. Even with a reduction in power, this engine was a good candidate for the heavy infantry tank.
The final promising engine was a version of the Paxman R-series marine diesel. Ricardo had mentioned this to him, as the way they were built allowed customisation of the number of cylinders. They had a number of advantages; they were built in a robust form (they supplied a version for the Navy to use in Submarines) that were resistant to shock, which would be a valuable trait for a tank engine. They could be produced to give around 500hp. The main issues would be weight and cost. Ricardo was very familiar with the design - they used the Comet head he'd designed in some of their engines- and he pointed out that setting up for a series production run would likely reduce the costs considerably.
While there were obvious problems with all the likely candidates, the problem now looked solvable. A decision was taken to investigate the three promising candidates more fully, and costs estimated for a run of either 250 or 500 engines. Even if the Army didn't want them all, the foreign market would likely be interested in more powerful tanks, and if not they could sell them for marine use. This was to be done as soon as possible so a decision could be made on usage. For his part, Sir John liked the look of the diesel Kestrel, if production could be arranged. Given its origin of Rolls-Royce and Ricardo, he felt reliability, a constant problem with high powered engines, wouldn't be an issue. 340hp should drive his idea of a Cruiser tank nicely, and one of the higher power engines would be a good fit for his Infantry tank idea. Given the much heavier weight the infantry tank was likely to be, he was starting to think that a common engine, while good for production, wouldn't be the best technical solution.
It does have nicer wing mirrors mindI've always been struck by the superficial resemblance of the recent German "Weisel" to the MkVI
From the Tank Encyclopedia:
Sometimes, the old becomes new again....
marathag
Banned
Germans, despite their love for complex systems, never went fot track bending for steering an AFV
Driftless
Donor
My thought was mostly on superficial appearance: very compact squat beetle-shaped body, High drive wheel in front sloping back to the ground level rear wheel. Other than that, not much is alike.
Now take a Mk VI and put one of those 500hp diesels in it.
We can get Louis Hamilton to drive it
We can get Louis Hamilton to drive it
January Vickers Meeting, Part 2
January 1936, Vickers Engineering. (part 2)
Having settled on the actions concerning engines, the next points were settle quickly. The suspension and steering were going to be the responsibility of Sir John and his department, and he already had ideas on how he was going to tackle them. The last part of the discussions was on the possible armament of the new generation of tanks.
Currently there was only one gun being used on British tanks, the low-powered 3pdr. While this had been adequate before the armour thickness of tanks had started to rise, it had been obvious for a while that it was no longer adequate. Over the last couple of years Woolwich and Vickers had been developing a new high-velocity 2pdr gun. Initial tests had shown it was capable of penetrating 30mm or armour at over 500 yards, and even at 1,000 yards it could nearly penetrate. Given the thickness of armour they were working on, 30mm was the assumption of the protection of an enemy tank. While the initial results were promising, a better long range penetration was considered desirable, and now the gun was starting to come off the production line, effort was going to be put into improving the shells.
When the 2pdr had been proposed as the new infantry weapon, the conversations the Vickers team had had with the EAF officers indicated that while they liked the idea of a better 'hole-puncher', they would miss the HE capability of the new gun, as no HE rounds were currently envisaged. Although it had been suggested that HE would be helpful against enemy AT guns, this wasn't seen as a major issue. Although firing off a round or two might kill the AT gun, they expected that it would more likely be a diversion while they pulled back slightly and brought artillery fire down. They liked the old HE rounds more for the effect on soft-skin and rear element targets that were the main aim of their penetration and avoidance attacks. Given that it was expected that new enemy tanks would have thicker armour, Vickers had suggested that once the 2pdr was ready, a larger 3pdr version could be made fairly easily based on the 2pdr design. This would still allow the old HE to be used, but would give them an edge in tank-on-tank combat. There had been no problems in the upgraded size, and a version was now being tested, and was showing considerable improvement over the 2pdr. The 2pdr was still seen as a better infantry weapon, the 1935 exercises had show a low weight was very helpful, but this was far less of a problem for a tank gun,
While this gave Carden a good gun for the new tanks, he wanted to discuss other, larger weapons. He was looking to make a tank that could be upgraded to a larger gun when that became necessary - while not cheap, replacing the gun was a lot cheaper than building a whole new tank. He was particularly interested in the Army's concept of a tank directly supporting infantry, and aiding in the breakthrough. The 3pdr wouldn't be the ideal gun for this, what seemed to be needed was a large calibre gun firing HE. This would be used directly against targets like machine gun, anti-tank guns and fixed defences such as pillboxes. While of course artillery would also be available, exercises had shown that being able to respond instantly was very useful, as small or individual targets could be taken out and bypassed quickly, especially if the artillery was otherwise engaged. The large calibre would give the gun the ability to fire an effective smoke round, either in support of an infantry attack or to allow the armour to retreat to a holding position while the artillery was called in. While the RTC weren't embedded in the 'Charge It!' philosophy of the old Cavalry units, they did realise that speed in attack caused more progress and fewer casualties to their own side. It also helped cause confusion and disarray, things most helpful in their aim of forcing open a weak point to exploit.
While no-one had any real disagreements about the need for a large calibre gun, there were lots of arguments about what exactly the gun should be. What they needed was a gun that could fire a good HE shell, as well as a good smoke round. While not seen as a major role, a few AT rounds, just in case, was also seen as a useful addition.
The first suggestion was the QF 3" howitzer. This was a low-velocity weapon, firing a 14lb shell. While the shell weight was considered adequate for HE and smoke, there was concern that the low m/v meant it would be useless against tanks or pillboxes. However the gun was available, although there were worries about what the Royal Artillery would say about tanks carrying what they would see as 'one of OUR guns'! There was concern that this was quite an old design, and that there might be resistance to putting an 'old' gun in a 'new' tank.
From the point of view of effectiveness, the current 18pdr, which was going to be replaced shortly by a 25pdr, would be ideal. It had all the types of round needed already in production, and ammunition would be common to that used by the artillery. The problem was the recoil length. No-one had ever envisaged using this gun inside a turret, and unless a way could be found to considerably shorten the recoil length, the size of turret needed to accommodate it would be prohibitively large and heavy, not to mention needing a bigger tank to carry it.
The long recoil of most of the large calibre candidates was the biggest argument against using one of them. However after some rather heated discussion, one of the engineers working on the naval guns came up with a possible solution. Vickers had been working on a new 6pdr gun for the Royal Navy, to replace the older version. It had gone into production in 1934, so a few could easily be made for testing. The gun itself weight just over 1,000lb, which was rather heavier than they had considered, but it was pointed out that it could be lightened a bit - weight was less of an issue for naval guns than robustness. Of course, a 6pdr round wasn't big enough for the sort of shell they were looking for, so it was suggested they bore it out to 3.3" so it could take modified 18pdr ammunition. Secondly, they could reduce the barrel length - the naval gun had a m/v of 2,400fps, which was actually higher than ideal. The naval version was 45 calibres long, and reducing this to something around 30 would make it easier to machine, reduce the weight, and allow the use of a less powerful HE shell that would allow more HE to be included. While the navy did have an HE shell for the gun, the usage and requirements of the navy for their HE rounds were somewhat different. Something around 1,500fps might be suitable, and even with the lower velocity, an AT round of this size would have significant penetration - a few hurried calculations suggested that it would be at least as good as the new 3pdr, although the more curved trajectory would probably make it less accurate. Since using the gun against tanks wasn't seen as the primary purpose, this should be acceptable. Furthermore, the gun only had a recoil of 12", which shouldn't be too hard to fit into a turret.
For his part, the idea interested Sir John. While the current 3pdr was a good tank gun, once they had the infantry tank in production other nations would surely follow their example, and the 3pdr wouldn't be good enough at any sort of range. When that happened, a larger gun would be needed in the anti-tank role, and the full length version of the 6pdr would probably do very nicely. He was a believer in making tanks that could be upgraded where feasible, and if a turret could take the bored out 6pdr, it could also handle the original gun. A 3.3" round would make a very satisfactory support weapon, assuming of course the Army were interested. From the talks he'd had with them, he thought they could be persuaded, and he started making notes on using this gun in his infantry tank design.
Having settled on the actions concerning engines, the next points were settle quickly. The suspension and steering were going to be the responsibility of Sir John and his department, and he already had ideas on how he was going to tackle them. The last part of the discussions was on the possible armament of the new generation of tanks.
Currently there was only one gun being used on British tanks, the low-powered 3pdr. While this had been adequate before the armour thickness of tanks had started to rise, it had been obvious for a while that it was no longer adequate. Over the last couple of years Woolwich and Vickers had been developing a new high-velocity 2pdr gun. Initial tests had shown it was capable of penetrating 30mm or armour at over 500 yards, and even at 1,000 yards it could nearly penetrate. Given the thickness of armour they were working on, 30mm was the assumption of the protection of an enemy tank. While the initial results were promising, a better long range penetration was considered desirable, and now the gun was starting to come off the production line, effort was going to be put into improving the shells.
When the 2pdr had been proposed as the new infantry weapon, the conversations the Vickers team had had with the EAF officers indicated that while they liked the idea of a better 'hole-puncher', they would miss the HE capability of the new gun, as no HE rounds were currently envisaged. Although it had been suggested that HE would be helpful against enemy AT guns, this wasn't seen as a major issue. Although firing off a round or two might kill the AT gun, they expected that it would more likely be a diversion while they pulled back slightly and brought artillery fire down. They liked the old HE rounds more for the effect on soft-skin and rear element targets that were the main aim of their penetration and avoidance attacks. Given that it was expected that new enemy tanks would have thicker armour, Vickers had suggested that once the 2pdr was ready, a larger 3pdr version could be made fairly easily based on the 2pdr design. This would still allow the old HE to be used, but would give them an edge in tank-on-tank combat. There had been no problems in the upgraded size, and a version was now being tested, and was showing considerable improvement over the 2pdr. The 2pdr was still seen as a better infantry weapon, the 1935 exercises had show a low weight was very helpful, but this was far less of a problem for a tank gun,
While this gave Carden a good gun for the new tanks, he wanted to discuss other, larger weapons. He was looking to make a tank that could be upgraded to a larger gun when that became necessary - while not cheap, replacing the gun was a lot cheaper than building a whole new tank. He was particularly interested in the Army's concept of a tank directly supporting infantry, and aiding in the breakthrough. The 3pdr wouldn't be the ideal gun for this, what seemed to be needed was a large calibre gun firing HE. This would be used directly against targets like machine gun, anti-tank guns and fixed defences such as pillboxes. While of course artillery would also be available, exercises had shown that being able to respond instantly was very useful, as small or individual targets could be taken out and bypassed quickly, especially if the artillery was otherwise engaged. The large calibre would give the gun the ability to fire an effective smoke round, either in support of an infantry attack or to allow the armour to retreat to a holding position while the artillery was called in. While the RTC weren't embedded in the 'Charge It!' philosophy of the old Cavalry units, they did realise that speed in attack caused more progress and fewer casualties to their own side. It also helped cause confusion and disarray, things most helpful in their aim of forcing open a weak point to exploit.
While no-one had any real disagreements about the need for a large calibre gun, there were lots of arguments about what exactly the gun should be. What they needed was a gun that could fire a good HE shell, as well as a good smoke round. While not seen as a major role, a few AT rounds, just in case, was also seen as a useful addition.
The first suggestion was the QF 3" howitzer. This was a low-velocity weapon, firing a 14lb shell. While the shell weight was considered adequate for HE and smoke, there was concern that the low m/v meant it would be useless against tanks or pillboxes. However the gun was available, although there were worries about what the Royal Artillery would say about tanks carrying what they would see as 'one of OUR guns'! There was concern that this was quite an old design, and that there might be resistance to putting an 'old' gun in a 'new' tank.
From the point of view of effectiveness, the current 18pdr, which was going to be replaced shortly by a 25pdr, would be ideal. It had all the types of round needed already in production, and ammunition would be common to that used by the artillery. The problem was the recoil length. No-one had ever envisaged using this gun inside a turret, and unless a way could be found to considerably shorten the recoil length, the size of turret needed to accommodate it would be prohibitively large and heavy, not to mention needing a bigger tank to carry it.
The long recoil of most of the large calibre candidates was the biggest argument against using one of them. However after some rather heated discussion, one of the engineers working on the naval guns came up with a possible solution. Vickers had been working on a new 6pdr gun for the Royal Navy, to replace the older version. It had gone into production in 1934, so a few could easily be made for testing. The gun itself weight just over 1,000lb, which was rather heavier than they had considered, but it was pointed out that it could be lightened a bit - weight was less of an issue for naval guns than robustness. Of course, a 6pdr round wasn't big enough for the sort of shell they were looking for, so it was suggested they bore it out to 3.3" so it could take modified 18pdr ammunition. Secondly, they could reduce the barrel length - the naval gun had a m/v of 2,400fps, which was actually higher than ideal. The naval version was 45 calibres long, and reducing this to something around 30 would make it easier to machine, reduce the weight, and allow the use of a less powerful HE shell that would allow more HE to be included. While the navy did have an HE shell for the gun, the usage and requirements of the navy for their HE rounds were somewhat different. Something around 1,500fps might be suitable, and even with the lower velocity, an AT round of this size would have significant penetration - a few hurried calculations suggested that it would be at least as good as the new 3pdr, although the more curved trajectory would probably make it less accurate. Since using the gun against tanks wasn't seen as the primary purpose, this should be acceptable. Furthermore, the gun only had a recoil of 12", which shouldn't be too hard to fit into a turret.
For his part, the idea interested Sir John. While the current 3pdr was a good tank gun, once they had the infantry tank in production other nations would surely follow their example, and the 3pdr wouldn't be good enough at any sort of range. When that happened, a larger gun would be needed in the anti-tank role, and the full length version of the 6pdr would probably do very nicely. He was a believer in making tanks that could be upgraded where feasible, and if a turret could take the bored out 6pdr, it could also handle the original gun. A 3.3" round would make a very satisfactory support weapon, assuming of course the Army were interested. From the talks he'd had with them, he thought they could be persuaded, and he started making notes on using this gun in his infantry tank design.
Basically, a bored out Six Pounder, which is 30 calibres long with the new (old) 84mm 18 Pounder shell, so no a lot of visual change to the gun externally.
Edit: I think it's likely to be accepted simply from the fact that the 18 pounder shell has well and truly been debugged and there are likely massive war stocks left over from WW1.
Edit: I think it's likely to be accepted simply from the fact that the 18 pounder shell has well and truly been debugged and there are likely massive war stocks left over from WW1.
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It's basically because Vickers, having been talking to the tankies (who have been feeling a bit bolshie after the successful exercises of 34 and 35) are thinking a bit more along the lines of a multi-purpose gun rather than just a very low velocity HE-tosser.
The fact that the 6pdr is made by Vickers doesn't hurt, of course!
The fact that the 6pdr is made by Vickers doesn't hurt, of course!
Well, its a bit early for a 17pdr!
These two posts basically set the scene as far as Vickers is concerned for the next couple of years, but things are going to change from their current expectations. But they already have a good 3pdr and hopefully the new 18pdr, which are two of the best tank guns around in 1936. Of course, right now they haven't actually put a tank around them, but they are working on that