What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

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Gooner1
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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Gooner1 » 19 Nov 2018 17:14

MarkN wrote:
19 Nov 2018 16:32

RAC tankies, in particular, had been massively overclaiming. During Battleaxe, 4 and 7RTR alone overclaimed by almost 100 pantsers. How is any grownup decision-maker supposed to recognise that the 2-pdr is not doing the job on the battlefield when the user is saying it is! The user was firing too early and not doing the extent of damage that he claimed.
Did you never consider that the tankies and gunners were actually getting hits and even penetrations on the German tanks but the 2-pdr shot was such a feeble projectile that any damage caused could be soon repaired?
The 2-pdr remained an effective gun when used within its limits through to 1942 and beyond. However, by 1942, there were more effective guns out there which did a better job.
Well yeah, just look at that long list of user compliments ....
But it was less likely to shatter if it hit the pantser at a closer distance and in a less protected area.
Closer distance means higher velocity which can increase the chance of projectile shatter.
And?
And the British suffered a tank and anti-tank gun gap.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by MarkN » 19 Nov 2018 17:26

Gooner1 wrote:
19 Nov 2018 17:14
MarkN wrote:
19 Nov 2018 16:32
RAC tankies, in particular, had been massively overclaiming. During Battleaxe, 4 and 7RTR alone overclaimed by almost 100 pantsers. How is any grownup decision-maker supposed to recognise that the 2-pdr is not doing the job on the battlefield when the user is saying it is! The user was firing too early and not doing the extent of damage that he claimed.
Did you never consider that the tankies and gunners were actually getting hits and even penetrations on the German tanks but the 2-pdr shot was such a feeble projectile that any damage caused could be soon repaired?
Oh yes. The 2-pdr AP and APHE could well have punched into a pantser, rattled around inside and killed all the crew. The German recovery team could show up, clear out the bodies and new crew jump in with relatively minor disruption - depending on what damage was done inside. Oh yes, I've thought about that. But how did it come to pass. Oh yes, the British were normally the ones to vacate the battlefield thus allowing the Germans to recover not only their own tanks, but normally a good few working British tanks as well.

Problem with the gun or the user?
Gooner1 wrote:
19 Nov 2018 17:14
And the British suffered a tank and anti-tank gun gap.
A 'gap' exagerrated by post-war commentators with an axe to grind and (deliberately) not bothering to understand the reality.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Gooner1 » 19 Nov 2018 17:51

MarkN wrote:
19 Nov 2018 17:26
A 'gap' exagerrated by post-war commentators with an axe to grind and (deliberately) not bothering to understand the reality.
From the German 'Manual of the British Army' April 1942:
"[British} Armoured troops have attacked with determination in spite of the German superiority in armament, of which they are aware.'

I expect you think you understand the reality better than them! :lol:

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Don Juan
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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Don Juan » 19 Nov 2018 18:25

Here's a table that the British produced to show the (in)effectiveness of their tank guns against the main German medium tanks:

Table 4.jpg

Item No.3 is the Panzer III Ausf. H and item No.4 is the Panzer III Ausf. J

However, I have not seen an equivalent table showing how effective or not the 5cm was against British tanks. Using Liddell-Hart's figures against the main British-made tanks, and using the standard German APCBC-HE ammunition, I reckon that the 5cm KwK 39 in the Panzer III was roughly this effective:

Matilda

Front (75mm) Nil
Side (65mm) Nil

Valentine

Front (60mm) <200x
Side (60mm) <200x

Crusader

Front (50mm) <500x
Nose Plate (32mm) <1500x

(These figures at 30 deg.)

If Liddell-Hart's figures are correct, it shows that the 5cm KwK 39 was only really effective against a limited portion of the front of the Crusader. The following picture shows the portions of the front of the Crusader that fell below the nominal 50mm basis, highlighted in a lovely shade of lilac:

crusader_mk2.JPG

These areas are the nose plate (lowest), the parts of the driver's front plate not covered by the cast visor and revolver port, and the nearside upper front plate. However, this latter plate would have been additionally covered by the hull MG turret (whether occupied or not) up until Spring 1942. Nonetheless, these are the areas that German gunners would have had to have aimed for if they wanted to disable the Crusader from a distance.

Now, one thing that is missing from the British table is that although the Panzer III Ausf. H had the front of its hull built up to 60-62mm with face hardened plates, my understanding (which may or may not be correct) is that its front turret plates remained at 30mm thick, and its gun mantlet remained at 35mm thick. I don't know how the armour in this area worked, but if these were the actual thicknesses, this implies that the turret of the Ausf. H was vulnerable to the 2 pounder at 1000x to 1500x.

I have not seen any documents generated by the RAC or the GHQ(AFV) in Cairo that mention the turret front as a vulnerable area, which is curious, and it would be interesting to know if the RA had anything to say about it. However, if this area was indeed in the 30 to 35mm range of thickness, it would mean that the Panzer III Ausf. H was at least as vulnerable at range as the Crusader. And if this was considered to be too small an area to deliberately target at long range by the British, why would the Germans attempt to target the small vulnerable plate area of the Crusader at long range?

Is it the case then that the real difference was not in the relative effectiveness of the tanks, but in the fact that the Germans effectively coordinated their tank and anti-tank units, whereas the British didn't?
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"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by MarkN » 19 Nov 2018 18:45

Gooner1 wrote:
19 Nov 2018 17:51
MarkN wrote:
19 Nov 2018 17:26
A 'gap' exagerrated by post-war commentators with an axe to grind and (deliberately) not bothering to understand the reality.
From the German 'Manual of the British Army' April 1942:
"[British} Armoured troops have attacked with determination in spite of the German superiority in armament, of which they are aware.'

I expect you think you understand the reality better than them! :lol:
Really? That's how you evidence your opinion..... :lol:

On 18 November 1941, 22nd Armoured Brigade in Cruiser Mk.VI pantsers attacked the Italian positions around Bir el Gubi. They got torn apart by Italian 4.7mm ATk guns and the same 4.7mm installed in M.13 pantsers. It was the very same 4.7mm gun that had not proven to be any major concern during Op Compass 9-11 months earlier. The M.13 was the same tank too.

When the British employed about 60 captured M.13, they contrived to lose all of them whilst barely firing a shot in anger.

The performance of the 4.7mm Italian gun had not changed. The Cruiser Mk.VI was a better armed tank than the majority of those used during Op Compass (Cruisers Mk.I, Mk.II and Mk.IV). In theory, the tank v anti-tank gap had widened in the favour of the British. And yet..... :roll:

The evidence suggests that battlefield results have more to do with the user than the equipment.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Don Juan » 20 Nov 2018 12:59

Here's another reference to the captured German performance figures for the 5cm KwK 39, as referenced in Liddell-Hart's letter to Colonel Cooper:

Table 5.jpg

This indicates that the 5 cm KwK 39 was very slightly more powerful than the 2 pdr, in contrast to the figures given in the Official History. The online version of the Official History does not give the source of their figures sadly, although I wonder if the original print copy does. Using the Germans' own figures, I would amend the estimated performance of this gun, using standard ammunition, against British tanks as follows:

Matilda

Front (75mm) Nil
Side (65mm) Nil

Valentine

Front (60mm) <100x
Side (60mm) <100x

Crusader

Front (50mm) <600x
Nose Plate (32mm) <1500x

This indicates that both the Matilda and Valentine were much more dangerous to the Panzer III Ausf. H than vice-versa, although of course British doctrine dictated that these two tanks were to be kept away from tank vs. tank actions. Liddell-Hart assumes that the turret front of the Ausf. H was indeed on a 35mm basis, and considers that this tank was vulnerable as long as any attacker knew that they needed to aim for the turret - something that during Operation Crusader the British would not have known, as they were generally unaware of the additional hull armour. Nonetheless, the statement of HQ RA 1 Armd Div that all German tanks were vulnerable to 2 pdr at 1000 yards appears to be, strictly speaking, correct.
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"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
- 7th Armoured Brigade War Diary, 30th August 1941

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Gooner1 » 20 Nov 2018 13:55

Don Juan wrote:
20 Nov 2018 12:59
This indicates that the 5 cm KwK 39 was very slightly more powerful than the 2 pdr, in contrast to the figures given in the Official History. The online version of the Official History does not give the source of their figures sadly, although I wonder if the original print copy does. Using the Germans' own figures, I would amend the estimated performance of this gun, using standard ammunition, against British tanks as follows:

Matilda

Front (75mm) Nil
Side (65mm) Nil

Valentine

Front (60mm) <100x
Side (60mm) <100x

Crusader

Front (50mm) <600x
Nose Plate (32mm) <1500x
The problem here is that those penetration figures are calculated at an angle of 30° from the vertical, meaning more armour to pass through than if it were a vertical plate.
There's an online calculator somewhere where you can work out the multiplier based on the armour slope, but off my head a multiple of about 1.3 to work out pen. of a vertical plate from one at 30°

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Don Juan » 20 Nov 2018 14:07

Gooner1 wrote:
20 Nov 2018 13:55
The problem here is that those penetration figures are calculated at an angle of 30° from the vertical, meaning more armour to pass through than if it were a vertical plate.
There's an online calculator somewhere where you can work out the multiplier based on the armour slope, but off my head a multiple of about 1.3 to work out pen. of a vertical plate from one at 30°
This is true, but there wasn't much vertical armour on the front of the Matilda and Valentine, and of course some of the sloping plates were nominally thinner, the angle of slope providing the basis. In any case, I think with these two tanks the Germans would have switched to Pzgr.40 and hoped for the best.

I'm not being definitive with any of this, because there may be figures out there that suggest the 5cm KwK 39 was more powerful than the figures I have provided. I'd also like definitive confirmation of the armour of the Pz.III Ausf.H turret front. However, from the information I have, which is imperfect, I don't see any notable superiority for the 5cm KwK 39 over the 2 pounder, or indeed of (some of) the tanks they were mounted in.
"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
- 7th Armoured Brigade War Diary, 30th August 1941

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by MarkN » 20 Nov 2018 15:52

Gooner1 wrote:
20 Nov 2018 13:55
The problem here is that those penetration figures are calculated at an angle of 30° from the vertical, meaning more armour to pass through than if it were a vertical plate.
That's NOT what the document says, but it's probably true... :wink:
Angle of attack is not given, but this is thought to be 30°.
Anyway, some for those interested to enjoy as bedtime reading...

Image

Image

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Gooner1 » 20 Nov 2018 16:01

Don Juan wrote:
20 Nov 2018 14:07
This is true, but there wasn't much vertical armour on the front of the Matilda and Valentine, and of course some of the sloping plates were nominally thinner, the angle of slope providing the basis. In any case, I think with these two tanks the Germans would have switched to Pzgr.40 and hoped for the best.
Switched to the PzGr.40 or trundled slowly backwards to lure the I tanks into the range of the 88s and Pak 38s. It's nice to have options.
I'm not being definitive with any of this, because there may be figures out there that suggest the 5cm KwK 39 was more powerful than the figures I have provided. I'd also like definitive confirmation of the armour of the Pz.III Ausf.H turret front. However, from the information I have, which is imperfect, I don't see any notable superiority for the 5cm KwK 39 over the 2 pounder, or indeed of (some of) the tanks they were mounted in.
Well the 5cm projectile had twice the mass of the 2-pdr, it also had a small bursting charge, which meant any after penetration damage was likely to be greater. Then it had a cap which made it less likely to shatter on hitting armour than the miserable 2-pdr shot.

Good question on the PzIII H turret front. I've seen a max of 37mm armour for model F and 50mm for the model J, dunno about the H, but considering the quantity of 2-pdr shot at the German tanks, if the turret was vulnerable I'm sure it would have become common knowledge.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by MarkN » 20 Nov 2018 16:18

A wall of words to highlight a point.

Two allies use the very same ATk gun and the very same rounds. They are fighting a common enemy. However, whilst the actual gunners are of equal capability and competence, the two allies have somewhat differing doctrine and combat tactics.

Ally (A) has a 'defeat the enemy' approach. Their battle drills are to site their ATk gun on the ground and to camouflage it as best possible and hold the line. They are to engage the enemy at no greater distance than 1,000yds and to remain engaging the enemy until ordered to withdraw.

Ally (B) has a 'don't be defeated by the enemy' approach. Their battle drills are to have their ATk gun portee and to use mobility to avoid being killed. They are to engage the enemy starting at 1,500yds and to disengage when the enemy gets to 1,000yds distance, and withdraw to the next firing line and repeat process.

In the first round of fighting, the enemy has a pantser with armor that can be penetrated by the ATk gun with 80% probability at 1,500yds range. In this round of fighting, both (A) an (B) report excellent results. (A) suffers a few more casualties than (B) but gives up no ground whilst (B) conceedes on average about 4 miles per battle.

In the second round of fighting, the same enemy has the same pantser but has now bolted on some additional frontal armor. Now, there is only an 80% probability of penetration by the ATk gun at 900yds. In this round of fighting, (A)'s battle report is little different from the first round of fighting. However, (B)'s battle report simply states - after losing the whole front - that the gun is absolutely worthless!!!

The effectiveness of the ATk gun has not changed. It is the way that it is being used that defines its battlefield success.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Don Juan » 20 Nov 2018 17:02

MarkN wrote:
20 Nov 2018 15:52
Anyway, some for those interested to enjoy as bedtime reading...

Image

Image
These graphs reveal that the figures for the 5cm KwK 38, which correlate with those quoted in the Official History, were derived from Ordnance Board Proceeding (i.e. trial) Q1834 of 19th January 1944. As these proceedings would have been conducted in controlled conditions against standard British plate, the results gained should be viewed as more reliable than the German figures, with the caveat that it is likely that as a captured weapon would have been used, it may have had a notably worn barrel.

Therefore I think that both the German and British figures provide a pretty reliable ball park for the 5 cm Kwk 39's performance.
"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
- 7th Armoured Brigade War Diary, 30th August 1941

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Juha » 20 Nov 2018 22:26

Don Juan wrote:
20 Nov 2018 12:59
Here's another reference to the captured German performance figures for the 5cm KwK 39, as referenced in Liddell-Hart's letter to Colonel Cooper:


Table 5.jpg


This indicates that the 5 cm KwK 39 was very slightly more powerful than the 2 pdr, in contrast to the figures given in the Official History. The online version of the Official History does not give the source of their figures sadly, although I wonder if the original print copy does. Using the Germans' own figures, I would amend the estimated performance of this gun, using standard ammunition, against British tanks as follows:

Matilda

Front (75mm) Nil
Side (65mm) Nil

Valentine

Front (60mm) <100x
Side (60mm) <100x

Crusader

Front (50mm) <600x
Nose Plate (32mm) <1500x

This indicates that both the Matilda and Valentine were much more dangerous to the Panzer III Ausf. H than vice-versa, although of course British doctrine dictated that these two tanks were to be kept away from tank vs. tank actions. Liddell-Hart assumes that the turret front of the Ausf. H was indeed on a 35mm basis, and considers that this tank was vulnerable as long as any attacker knew that they needed to aim for the turret - something that during Operation Crusader the British would not have known, as they were generally unaware of the additional hull armour. Nonetheless, the statement of HQ RA 1 Armd Div that all German tanks were vulnerable to 2 pdr at 1000 yards appears to be, strictly speaking, correct.
IMHO those figures are those of 5 cm KwK 38, the shorter L/42 barrel 5 cm tank gun, 5 cm KwK 39 was the longer barrel (L/60) tank gun which had performance similar to the 5 cm PaK 38. The L/60 tank gun appeared in later Pz III Ausf Js aka Pz III Specials as they were known By British.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by MarkN » 20 Nov 2018 23:19

Juha wrote:
20 Nov 2018 22:26
IMHO those figures are those of 5 cm KwK 38, the shorter L/42 barrel 5 cm tank gun, 5 cm KwK 39 was the longer barrel (L/60) tank gun which had performance similar to the 5 cm PaK 38. The L/60 tank gun appeared in later Pz III Ausf Js aka Pz III Specials as they were known By British.
Which figures?
a) The ones in the image provided by Don Juan
b) The figures in the link provided by Don Juan
c) His own typed conclusions

The data in the image is closer to the Pak38 data than the Kwk L/42 data in the link.

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Re: What prevented the QF 3.7-inch AA gun being used in the Anti Tank role.

Post by Don Juan » 20 Nov 2018 23:22

Juha wrote:
20 Nov 2018 22:26
IMHO those figures are those of 5 cm KwK 38, the shorter L/42 barrel 5 cm tank gun, 5 cm KwK 39 was the longer barrel (L/60) tank gun which had performance similar to the 5 cm PaK 38. The L/60 tank gun appeared in later Pz III Ausf Js aka Pz III Specials as they were known By British.
Yes, you're quite correct, Juha - I got the nomenclature wrong. I meant the 5 cm KwK 38 as fitted to the Pz. III Ausf. H and Ausf. J.
"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
- 7th Armoured Brigade War Diary, 30th August 1941

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