A34 Comet - how soon could it have been ready?

davebender said:

Britain received 17,000 sherman tanks. It's reliable and has decent cross country performance.

7.5cm/48 KwK 40 cannon fit into turret of 18 ton (original weight) Panzer IV. A similiar British made cannon should fit into larger Sherman turret without difficulty.

Germany welded 30mm RHA plates to front of Panzer IVG. Larger Sherman tank should support similiar 30mm RHA plates without difficulty.

Problem solved. Britain just needs to build Sherman upgrade kit which includes better main gun and add on frontal RHA. With these two upgrades surviving British Sherman tanks can serve into the early 1950s.

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The 'similar British made cannon' could be the 75mm HV or 77mm HV, however the British have made extra effort, with the 17pdr installed in the Sherman Firefly. An interesting proposal might be equipping the US built 3in/76mm cannons with APDS ammo, the AP performance should be along the 77mm HV.

This table might show why the Sherman was able to take the hefty powerful 17pdr - the turret ring was of generous dimensions (open the table in separate tab for hi-res):

WWII era APDS ammo was inaccurate to the point where a 1944 U.S. Army test concluded standard AP was overall superior. Germany must have reached a similiar conclusion as APDS ammo was not mass produced despite several development programs including APFSDS from smoothbore cannon. I prefer tank cannon able to hit the broad side of a barn so let's cross that option off the list.

HE capacity is just as important as AP. U.S. Army considered their 76mm HE shell to be poor. Perhaps a better HE shell could have been designed but if that were possible then why didn't it happen historically?

German 7.5cm/48 cannon has a good HE shell and decent AP performance in a relatively lightweight and inexpensive package. That's why it's my first choice for a WWII era tank / AT cannon.

British 77mm/50 cannon should work if Britain develops an effective HE shell for the weapon. Or else they could simply copy a captured German KwK40 cannon. Either way they need to get moving. British Sherman tanks should receive the upgrade before the end of 1943.

davebender said:

WWII era APDS ammo was inaccurate to the point where a 1944 U.S. Army test concluded standard AP was overall superior. Germany must have reached a similiar conclusion as APDS ammo was not mass produced despite several development programs including APFSDS from smoothbore cannon. I prefer tank cannon able to hit the broad side of a barn so let's cross that option off the list.

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The British, on the other hand, have concluded that APDS was a very useful thing, and it was the part of ammo supply for 3 gun calibers of the ww2. The 'regular' AP ammo still be carried in the tank, as it was probably practice in British army.

HE capacity is just as important as AP. U.S. Army considered their 76mm HE shell to be poor. Perhaps a better HE shell could have been designed but if that were possible then why didn't it happen historically?

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The 76mm HE shell was poor because it was consisted of too much steel and too little HE filler, being tailored to withstand the stresses when it was fired in the gun chamber. US Army can order the cartridge with reduced propellant (= less stress during firing), featuring the bigger/longer HE shell, with thinner walls much greater HE filler.
Why did it not happened? Well, it took some arms twisting to get the 76mm into Sherman, and 90mm was seen as the immediate future, so they thought why bother? Also, the HE and AP shells with almost the same ballistic properties could use the same sights - not the case when one is, say, 15 lbs, another is 10 lbs.

German 7.5cm/48 cannon has a good HE shell and decent AP performance in a relatively lightweight and inexpensive package. That's why it's my first choice for a WWII era tank / AT cannon.

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It is easy to like that gun.

British 77mm/50 cannon should work if Britain develops an effective HE shell for the weapon. Or else they could simply copy a captured German KwK40 cannon. Either way they need to get moving. British Sherman tanks should receive the upgrade before the end of 1943.

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By the end of 1943, the British have 17pdr in production for a year or so. Even with the APCBC ammo it can kill the Tiger under 1,5 km. The 75mm HV should allow for easier installation and greater ammo count, however. The 77mm HV was a later gun, 75mm HV and 17 pdr being earlier ones.

davebender said:

WWII era APDS ammo was inaccurate to the point where a 1944 U.S. Army test concluded standard AP was overall superior. Germany must have reached a similiar conclusion as APDS ammo was not mass produced despite several development programs including APFSDS from smoothbore cannon. I prefer tank cannon able to hit the broad side of a barn so let's cross that option off the list.

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6pdr and 77mm firing the same design as the 17pdr seemed to have no problems with APDS so it must have been a problem with compatability, rifling twist or chamber dimensions possibly

HE capacity is just as important as AP.

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In a tank HE is more important than AP a tanks job is infantry support 1st and tank fighting 2nd

German 7.5cm/48 cannon has a good HE shell and decent AP performance in a relatively lightweight and inexpensive package. That's why it's my first choice for a WWII era tank / AT cannon.

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Agreed excellent weapon probably the best all round tank gun of the war

British 77mm/50 cannon should work if Britain develops an effective HE shell for the weapon.

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An improved 76.2mm HE shell was available from about Sept 44

Or else they could simply copy a captured German KwK40 cannon.

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Copying a weapon built using metric measurements, different forging techniques and different steels isnt as easy as you think

davebender said:

WWII era APDS ammo was inaccurate to the point where a 1944 U.S. Army test concluded standard AP was overall superior. Germany must have reached a similiar conclusion as APDS ammo was not mass produced despite several development programs including APFSDS from smoothbore cannon. I prefer tank cannon able to hit the broad side of a barn so let's cross that option off the list.

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There was a bad batch of 17pdr APDS that got tested that seems to be widely quoted but it was not truly representative of the accuracy of APDS ammo. It may have been worse than regular AP ammo but it certainly able to hit tanks at combat ranges let alone barns. German's "must have reached a similar conclusion" is bogus. Germans had stopped production of APCR because of a shortage of tungsten. However well APDS may work or not work for long range artillery or AA use trying to use steel cores in APDS shot is near useless. They shatter on impact on armor anywhere near their theoretical penetration limit.

davebender said:

HE capacity is just as important as AP. U.S. Army considered their 76mm HE shell to be poor. Perhaps a better HE shell could have been designed but if that were possible then why didn't it happen historically?

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The HE shell was a left over AA shell. Tank armament is one area where the US had their heads up their butts. They wanted a shell with the same ballistics as the AP shell to simplify gunnery and training. High velocity HE shells means thick walls and low HE and or VERY good steel for the shell body.

davebender said:

German 7.5cm/48 cannon has a good HE shell and decent AP performance in a relatively lightweight and inexpensive package. That's why it's my first choice for a WWII era tank / AT cannon.

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A good choice but it got the HE capability by dropping the MV of the HE round to about 550 M/S, Less than a Sherman 75mm. No magic or German superiority, just a willingness to trade a bit of difficulty to use ( which can be solved with training) for a more effective overall system.

davebender said:

British 77mm/50 cannon should work if Britain develops an effective HE shell for the weapon. Or else they could simply copy a captured German KwK40 cannon. Either way they need to get moving. British Sherman tanks should receive the upgrade before the end of 1943.

Click to expand...

British need to adopt a shell with a much lower velocity than the AP round and/or make the shell out of better steel. If they copy the German KwK40 cannon and insist on make the HE round out of 19 ton steel and firing it at 750-790 M/S they will gain NOTHING over the guns they did use.

davebender said:

Britain received 17,000 sherman tanks. It's reliable and has decent cross country performance.

7.5cm/48 KwK 40 cannon fit into turret of 18 ton (original weight) Panzer IV. A similiar British made cannon should fit into larger Sherman turret without difficulty.

Germany welded 30mm RHA plates to front of Panzer IVG. Larger Sherman tank should support similiar 30mm RHA plates without difficulty.

Problem solved. Britain just needs to build Sherman upgrade kit which includes better main gun and add on frontal RHA. With these two upgrades surviving British Sherman tanks can serve into the early 1950s.

Click to expand...

Not into the 1950s. These were US tanks on loan and had to be given back after the war.

By the end of the war, Britain was procing better tanks than the Sherman. Not in the same numbers but I would rather have been in a Centurion than a Sherman.

I would rather be in a Tiger then a Panzer III. Such considerations miss the point that heavy tanks cost a lot of money.

Sherman tanks were free (for all practical purposes). All Britain must do is build a better gun that will easily fit in turret (i.e. not 17 pounder) and some additional frontal armor. Now they've got large numbers of an adequate MBT for no development costs (except main gun) and perhaps 20% of Centurion production cost.

It's interesting the testing of the Soviet T-34 KV-1 tanks. Though there seems to be some difference of opinion whether the examples used were of the battlefield and therefore 'worn' or off the production line therefore poor quality equipment!?
I wonder if their design, influenced the sloped armour on the Centurion!

As to the Comet - seems to me that it's design could be brought forward from July '43.
- Enigma traffic could have decoded the consternation felt by German units when they encountered the T-34 KV-1, at first the result would have been wry amusement, but later decodes could relate to German responses.
- intel from occupied Europe about new German large heavy tanks.
- encounters with the upgrades of the Panzer IV Tiger in Africa should have added more urgency than OTL.

So preliminary studies could have been done earlier, the Challenger design was drawn up in 1942 - why not the Comet.

If OTL deliveries start Sept '44, after testing in Feb '44. So IMHO plausible shave a month or three from the Feb to Sept., and bring design process to start late '42, which gives deliveries - with luck - a year earlier than OTL.

Can anyone stretch earlier than that?

The large numbers of Sherman that Britain had were Lend Lease were they not?
So at the end of the war, they would need to be handed back to the US.
So for Britain to have a credible tank post war - it was necessary for us to design and build it ourselves.