British Comet tank versus German panzers?

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Attrition
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Re: British Comet tank versus German panzers?

#31

Post by Attrition » 26 Nov 2009, 18:28

Attrition wrote:What happened to the 'new 75mm high velocity gun with a 50 calibre barrel' from Vickers-Armstrong?
Is this the one that became the 77mmHV?

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The_Enigma
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Re: British Comet tank versus German panzers?

#32

Post by The_Enigma » 27 Nov 2009, 00:02

Attrition wrote:
Attrition wrote:What happened to the 'new 75mm high velocity gun with a 50 calibre barrel' from Vickers-Armstrong?
Is this the one that became the 77mmHV?
Apparently, from the quick glance. I didnt use my own copy of the book i googled 75mm HV and it linked to the google book website. I will take a proper look over the weekend or something and report back.
When looking at pictures of the Sherman and Cromwell tanks, the turret on the Sherman seems smaller than the Cromwell.
Was the problem of fitting the 17pdr gun into the Cromwell not so much about the physical interior dimentions but one of the size of the tuttet ring?
ie: it fitted but the turret couldn't take the recoil.
As above, ill get back to you all soon about my "finding" :)


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Re: British Comet tank versus German panzers?

#33

Post by Wokelly » 27 Apr 2010, 06:07

Attrition wrote:What happened to the Vickers 75mm?
The Vickers HV 75mm never saw action. However the 75mm did ultimately become the 77mm. In short they took the modified breech design of the Vickers 75mm HV, attached it to the shortened barrel of the 17 pdr to make the 77mm, and used a 76.2mm projectile attached to a 3-inch 20 cwt casing to come up with the ammo. The essentially used the parts and ammunition from three guns to make the 77mm which must be something truly unique.

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Attrition
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Re: British Comet tank versus German panzers?

#34

Post by Attrition » 27 Apr 2010, 16:16

Thanks Wokelly. Do you have any sources on the Vickers gun?

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Re: British Comet tank versus German panzers?

#35

Post by Saxon Cross » 19 May 2010, 21:27

The Cromwell was fitted with the British OQF 75mm gun. It replaced the 6 pounder, because it fired a better HE round, but had worse AP performance than the 6 Pdr.

The 17 Pdr was fitted in the Firefly, Challenger, Archer and perhaps some others?

The Comet had the 77mm gun.

I looked up the AP performance for each gun, from several sources.
Penetration at 500yds using APCBC ammo, against armour at 30deg:

75mm: 7-10cm
77mm: 11-12cm
17Pdr: 13-14cm

Most sources give the 75mm a penetration of only 7-8cm. But it's possible that this was using the slightly inferior APC ammo.

The 77mm and the 17Pdr could fire sabots (which the 75mm could not) so the penetration of the 77mm and 17Pdr firing APDS would be around 18cm for the 77mm, and 20cm for the 17Pdr, at 500yds 30 deg.



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Re: British Comet tank versus German panzers?

#36

Post by speedythree » 03 Nov 2011, 20:28

I keep reading that the Comet’s 77 mm HV cannon was derived from the 17-pounder anti-tank cannon. But was this the case? I suspect that the 77 mm HV cannon was simply a Vickers-Armstrongs 75 mm HV cannon re-worked to take the same projectiles that were already in production for use in the ammunition for the 17-pounder.

“In March 1942 Vickers-Armstrong had offered a new, high-velocity 75mm gun with a 50-calibre barrel and there was a general belief that this would fit the new cruiser. It took until March 1943 to learn that it would not.” (Fletcher and Harley, Cromwell Cruiser Tank 1942-1950, Osprey Publishing Ltd., c2006, at p.14.) As a result, the Cromwell was initially equipped with the Mark V Ordnance QF 6-pounder; this would be replaced by the Ordnance QF 75 mm, which was developed from the 6-pounder. But what became of the 75 mm HV?

I don’t think that Vickers-Armstrongs would abandon this weapon to produce a totally new cannon based on a shortened 17-pounder barrel, fitted to a shortened breach and reworked to take ammunition made up of 17-pounder projectiles fitted to cases from the QF 3-inch 200-cwt cannon. I certainly don't believe that the British government would allow them to even try to do this in the middle of the Second World War. Instead, I think that VA continued to work on the 75 mm HV, enlarging the bore to that of the 17-pounder (76.2 mm). This would be much easier to do than starting a whole new project. Another reason I think this is the barrel length of the 77 mm HV, which, in the reading that I have done, is always given as 49 calibers. The 75 mm HV had a 50-caliber barrel, which would give the barrel an approximate length of 3750 mm (bore x length in calibers); if you divide that length by 76.2 mm, you get a barrel length of 49.2 calibers.

Then there is the matter of the cartridge case used with the 77 mm HV cannon, generally described as coming from the QF 3-inch 200-cwt cannon. This gun was a Vickers-designed anti-aircraft cannon introduced during the First World War and used well into the Second World War. Vickers-Armstrongs would have been very familiar with this ammunition case and would have had it in production. Was this case originally used with the 75 mm HV? (I have also read (on-line, no sources given) that 100 of these cannon were converted in 1941 to become QF 3-inch 16-cwt anti-tank guns. Was this done by VA and did these guns figure in the development of the 75 mm HV? Definitely questions to be researched further.)

I know that this is just conjecture; however, I find it to be much more persuasive than the idea of jury-rigging a gun from different sources (the 17-pounder was a Royal Ordnance product, not Vickers-Armstrongs) in just one year’s time. I intent to continue to research this topic to see what else I can find; anyone with further information, please comment.

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Re: British Comet tank versus German panzers?

#37

Post by speedythree » 24 Nov 2011, 00:16

A 3-inch 200-cwt cannon would be quite a thing to see (with one cwt or hundredweight equaling 112 pounds, this cannon would have a nominal weight of ten long tons.) The proper description is 3-inch 20-cwt.

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Re: British Comet tank versus German panzers?

#38

Post by RichTO90 » 24 Nov 2011, 00:31

speedythree wrote:I know that this is just conjecture; however, I find it to be much more persuasive than the idea of jury-rigging a gun from different sources (the 17-pounder was a Royal Ordnance product, not Vickers-Armstrongs) in just one year’s time. I intent to continue to research this topic to see what else I can find; anyone with further information, please comment.
It was jurry-rigged from different sources, but turned out to be a pretty good lash-up just the same. :) Essentially it was the barrel of the Vickers 75mm HV mated to the modified breech and chamber of the old 3" 20 cwt AA gun that fired the 17-pdr projectile mated to the 3" 20cwt cartridge. IIRC the driving band on the projectile was also modified to accomodate the difference between the 75mm bore and the 76.2 mm projectile, but I can't be sure off hand. Tony Williams would be the mand to check with. http://www.quarry.nildram.co.uk/

Cheers!
Richard Anderson
Cracking Hitler's Atlantic Wall: the 1st Assault Brigade Royal Engineers on D-Day
Stackpole Books, 2009.

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Re: British Comet tank versus German panzers?

#39

Post by speedythree » 01 Dec 2011, 09:41

I keep reading that the 77 mm HV comes from "different sources", but those sources (with perhaps one exception, the 3" / 76.2 mm projectiles it fired) all had one thing in common: they were all products of Vickers Ltd. and its successor, Vickers-Armstrongs, Ltd. That's why I have to wonder how much of the development of this weapon was evolutionary and how much was a result of jury-rigging. Was, as you say, the barrel of the 75 mm HV mated to the chamber and breech of the 3" 20 cwt cannon (i.e. discarding the original 75 mm HV chamber and breech) or was the 75 mm HV designed to use the 3" 20 cwt case right from the start? What was the development process? I am trying to get my hand on the book, Vickers : a history by J.D. Scott, to see what it has to say. But you are right, Tony Williams would be a good person to talk to about this.

Have a good day.

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