Best Tank of WW2

[Soren]

The Pzr IV weighs about 25 tons and has a 300hp engine and a top speed of 25mph while the Cromwell weighs about 28 tons and has a 600hp engine and a top speed of 40 mph. I wonder which one is more mobile. Can you name any medium tank with a higher power to weight ratio than the Cromwell?

Speed is not what defines how mobile a tank is, and neither is the hp of the engine vs the weight of vehicle. What matters most is the torque available vs the weight of vehicle and how it is transferred through to the tracks, plus what type of track suspension design is used. The narrow tracks of the Cromwell will limit mobility in some key inviroments such as muddy snowy terrain. If the Pz.IV was fitted with its wide tracks I suspect the Cromwell wasn't any more mobile.

Please provide some comparative data AP data for the 75mm L48 versus the 6pdr.

7.5cm KwK40 L/48 performance against vertical 240 BHN RHA armour plates:
Projectile: 6.8 kg PzGr.39 APCBC(HE)
MV: 792 m/s
100m = 135mm
500m = 123mm
1,000m = 109mm
1,500m = 97mm
2,000m = 86mm
2,500m = 76mm
3,000m = 68mm

5.7cm 6pdr L/52 performance against vertical 240 BHN RHA armour plates:
Projectile: 3.23 kg Mk.9T APCBC
MV: 831 m/s
100m = 115mm
500m = 103mm
1,000m = 90mm
1,500m = 78mm
2,000m = 68mm
2,500m = 60mm
3,000m = 52mm

As can clearly be seen the German 7.5cm KwK40 L/48 is a superior anti tank gun with the std. armour piercing ammunition used by both guns, being powerful enough to punch through the thickest part of a the Cromwell (76mm front) at ranges as great as 2,500m and even beyond seeing as the Cromwell's armour was very brittle at 400 to 450 BHN. The Cromwell will however struggle against the Panzer IV Ausf.G H's 80mm frontal armour, the 6pdr only being capable of defeating it within a range of 1,500m with its std. armour piercing round.

 

[parsifal]

The debate regarding mobility is incomplete by a wide margin. Even defining what sort of mobility you are talking about needs to be clarifed....tactical or technical mobility, operational mobility or strategic mobility, for a start.

I suggest some further reading on the issue, and as a start refer you to the following link

http://www.hrbi.hr/_images/files/izdavastvo_55.pdf

 

[Soren]

Fully agreed, that's what I was pointing out as-well.

 

[Juha]

Oh Soren
Now you are claiming that penetration info against 240RHA can be used without any calculations as equivalent to penetration against GB tank armour.

Not surprisingly German figures for 7,5cm Pak 39, the gun of Hetzer which had the same performance than the PzIVH's KwK 40, with side angle of 30deg, are smaller and that is true even when we take into account the 30deg side angle, its PzGr. 39 penetrates Cromwell turret front up to 1000m, mantle up to 1600m, driver's front plate 1800m and nose up to 1400m.
And BTW Pz IVG's H's turret front armour was only 50mm, so?

On mobility, Finns were not overly impressed on PzIVJ's mobility and Charioteer, a Cromwell with a new turret with 20pdr (83mm, the mother of the Nato 105mm tank cannon) was fairly mobile in rather deep snow. I know, I have got a drive on one in the middle of Finnish winter and fought against them in the middle of Finnish winter during military exercises.

On the other hand KwK 40 had a good HE round, 6pdr had not.

Juha

 

[Vincenzo]

saw the figure either 6pdr and kwk 40 are versus same armour so it's right the kwk 40 was best. the range of soren it's not real world range but for both. 80mm for PZ IV it's for hull (and soren don't write that were for turret)

 

[Soren]

Oh Soren
Now you are claiming that penetration info against 240RHA can be used without any calculations as equivalent to penetration against GB tank armour.

No Juha, I never claimed that, esp. since I actually know what difference it makes. Now if you actually understood the effects of BHN relative to the penetration performance of AP projectiles you would've never made that comment. It might surprise you to know that a RHA plate of >70mm thickness with a BHN of 240 is more resistant to APCBC projectiles than one of 400 to 450 BHN of the same thickness.

Not surprisingly German figures for 7,5cm Pak 39, the gun of Hetzer which had the same performance than the PzIVH's KwK 40, with side angle of 30deg, are smaller and that is true even when we take into account the 30deg side angle, its PzGr. 39 penetrates Cromwell turret front up to 1000m, mantle up to 1600m, driver's front plate 1800m and nose up to 1400m.
And BTW Pz IVG's H's turret front armour was only 50mm, so?

Ok that made exactly zero sense to me. I posted the peformance of the gun against vertical 240 BHN RHA plates which are tougher than the armour of the Cromwell. So yes, the 7.5cm KwK40 will infact punch a hole in the 76mm front armour of the Cromwell at 2,500m and beyond with the PzGr.39.

On mobility, Finns were not overly impressed on PzIVJ's mobility and Charioteer, a Cromwell with a new turret with 20pdr (83mm, the mother of the Nato 105mm tank cannon) was fairly mobile in rather deep snow. I know, I have got a drive on one in the middle of Finnish winter and fought against them in the middle of Finnish winter during military exercises.

You haven't tried both so your opinion on this is worthless really. Furthermore when you say that the Finns weren't overly impressed with the mobility of the Pz.IV you're implying they actually had something negative to so say about it, so did they? I'm interested in this since the Pz.IV was regarded as a pretty mobile tank, one designed for the concept of BlitzKrieg.

I sincerely doubt that the Cromwell was more mobile than the Pz.IV over very muddy or snowy terrain.

 

[Juha]

Now IMHO German figure of 7,5cm Pak 39 being capable to penetrate the turret of Cromwell up to 1000m when side angle is 30deg is not comparable to your claim that KwK 40 using same ammo was capable to penetrate the turret of Cromwell from over 2500m head on. So do you believe German figures or not?

And as I wrote 6pdr should only to be capable to penetrate 50mm to knock out late Pz IV, so it seems that 6pdr Cromwell could penetrate the turret of Pz IV from longer range than late Pz IV could penetrate the turret of Cromwell, but that was mostly theoretical advantage, both could penetrate other's turret at normal battle ranges in NW Europe.

On Finnish oppinion on cross country mobility of PzIVJ, IIRC it was not very high, but the yardstick was T-34.

I have seen and ride on Charioteer in snowy conditions but not in muddy condition. The snow was rather deep say 50cm.

Juha

 

[DerAdlerIstGelandet]

You haven't tried both so your opinion on this is worthless really.

No ones opinion is worthless!

 

[dunmunro1]

LoL, I wonder which was more " mobile" over the typical conditions in western Europe? Your argument that the Mk IV "might" be more mobile under a very narrow set of circumstances is pretty weak.

What is your source for the AP data? It looks like the 6 pdr results are for a 30 deg target angle. Here's some data from the WW2 Equipment site: WWII Equipment.com

6 pdr Mk IV/V APCBC 2780fps Target Angle=30 Armour=MQ 500yds =86mm 1000yds=80 2000yds= 68

Pak 40 Pzgr 39 (APCBC) 792m/s TA 30 Armour =MQ 500m=96mm 1000m = 85 2000m= 64

and this is very close to the data here: 7,5 cm Kampfwagenkanone 40 L/48, 7,5 cm Panzerabwehrkanone 40 L/48 and 7,5 cm Sturmkanone 40 L/48

so your data differs widely from the above. The 75mm gun has only a small advantage, decreasing with range.

BTW, here is a US Army report on firing trials of the 6 pdr versus a Panther:
http://efour4ever.com/57mm.htm

 

[Vincenzo]

I commonly reading that heavy shell it's best a long range it's strange that kwk 40 loss comparate with the 6pdr as the range longer

 

[dunmunro1]

I commonly reading that heavy shell it's best a long range it's strange that kwk 40 loss comparate with the 6pdr as the range longer

It may be that the Ballistic Cap for the 6pdr had more efficient aerodynamics, and thus a smaller drop in Striking Velocity.

 

[Soren]

LoL, I wonder which was more " mobile" over the typical conditions in western Europe? Your argument that the Mk IV "might" be more mobile under a very narrow set of circumstances is pretty weak.

What is your source for the AP data? It looks like the 6 pdr results are for a 30 deg target angle. Here's some data from the WW2 Equipment site: WWII Equipment.com

My source is actual test results obtained at the Aberdeen Proving Grounds USA, as listed in the book WW2 armor Gunnery by Robert D. Livingston Lorrin Rexford Bird.

And the reason the figures are higher than elsewhere for both guns is that the US tests were carried out against plates at a 90 degree angle (vertical), as apposed to the 30 degree std. in German British tests. Furthermore, as explained by Robert D. Livingston, the Germans tested their guns against tougher and higher quality plates than other countries, and placed a more strict criteria on what was to be determined a successful penetration. Hence why both the US British achieved higher penetration results with captured German guns in their tests than the Germans did with in their own tests, the reason being that the Germans were firing against tougher plates of higher quality and had a more strict criteria for penetration.

German definition of a penetration:
2/3rds (66.6%) of all projectiles fired must penetrate completely through the plate.

British definition of a penetration:
1/2 (50%) of all projectiles fired must penetrate completely through the plate.

US definition of a penetration:
1/2 (50%) of all projectiles fired need only partially penetrate the plate.


German test results with 7.5cm KwK40 L/48 against 265 BHN RHA armour plate laid back 30 degrees:
Projectile: 6.8 kg PzGr.39 APCBC(HE)
MV: 792 m/s
100m = 106mm
500m = 96mm
1,000m = 85mm
1,500m = 74mm
2,000m = 64mm
2,500m = 56mm
3,000m = 49mm

British test results with 5.7cm 6pdr L/52 against 279 BHN RHA armour plate laid back 30 degrees:
Projectile: 3.23 kg Mk.9T APCBC
MV: 831 m/s
91m = 89mm
457m = 81mm
914m = 74mm
1,371m = 63mm
1,828m = 56mm
2,286m = 50mm
2,743m = 44mm

Sources:
WW2 Armor Gunnery by Robert D. Livingston and Lorrin R. Bird.
Panzerkampfwagen IV Ausf.G, H and J 1942-45 by Thomas L. Jentz Hilary L. Doyle

so your data differs widely from the above. The 75mm gun has only a small advantage, decreasing with range.

Which is because your data is wildly wrong.

 

[Soren]

It may be that the Ballistic Cap for the 6pdr had more efficient aerodynamics, and thus a smaller drop in Striking Velocity.

No its just that your data is wrong. The 7.5cm 6.8kg APCBC projectile retains velocity better than the 5.7cm 3.23 kg APCBC projectile.

 

[Soren]

Now IMHO German figure of 7,5cm Pak 39 being capable to penetrate the turret of Cromwell up to 1000m when side angle is 30deg is not comparable to your claim that KwK 40 using same ammo was capable to penetrate the turret of Cromwell from over 2500m head on. So do you believe German figures or not?

Are you talking about the calculated German figures against an enemy tank standing at a 30 degree angle, or the actual real life test results they obtained against high quality RHA plates laid back 30 degrees? Cause the actual tests only support the US test figures I've supplied so far.

In short I trust the German, US British test figures 100% as they are real life results and the parameters are clear.

 

[Soren]

No ones opinion is worthless!

How can you compare two cars if you've only driven one of them Adler? It's that simple really.

I've driven a T-55, a Leopard Centurion, but my actual experience of their mobility aint really worth much as my experience in them is very limited to say the least, having probably 20min behind the controls in each of them. And if I was to compare them to a tank I've never even sat in then my opinion would be worthless.

I think you're misinterpreting a simple stating of fact as an attempt at being rude, not so.

 

[DerAdlerIstGelandet]

How can you compare two cars if you've only driven one of them Adler? It's that simple really.

I've driven a T-55, a Leopard Centurion, but my actual experience of their mobility aint really worth much as my experience in them is very limited to say the least, having probably 20min behind the controls in each of them. And if I was to compare them to a tank I've never even sat in then my opinion would be worthless.

I think you're misinterpreting a simple stating of fact as an attempt at being rude, not so.

You know what my point was...

 

[Soren]

I thought you meant I was being rude Adler, which wasn't what I wanted, just wanted to point out that unless one has experience in both vehicles then ones opinion on the matter is worthless. Truth is that Juha I can only guess how these two tanks compare in terms of mobility, and my guess is that they were rather close overall.

 

[Soren]

Anyway all this talk of tank guns and their performance has urged me to post a complete list of data on the most numerous tank guns used during WW2 in a seperate thread. It will be up soon, either today or tommorrow

 

[dunmunro1]

Which is because your data is wildly wrong.

LOL!, did you not read the data in the image that I posted? It shows the 6 pdr APCBC penetrating the 82mm Tiger turret side armour at 30deg target angle @ 600yds! According to your data this isn't possible!

 

[Soren]

LOL!, did you not read the data in the image that I posted? It shows the 6 pdr APCBC penetrating the 82mm Tiger turret side armour at 30deg target angle @ 600yds! According to your data this isn't possible!

You do realize that the Tiger's turret is curved on the sides right? That means there's a high probability of the projectiles impacting the armour at a 90 degree angle despite the 30 degree side angle to the hull. At 90 degrees the 6pdr Mk.9T will penetrate 102mm of 240 BHN RHA armour at 540 meters (600y), making it capable of penetrating the Tiger's sides from that range. That would explain the results.

Also you should not forget the rules of physics at play here, the penetration performance of a projectile very much depends on how much kinetic energy you can concentrate in as small an area as possible; Hence why subcaliber sabot rounds are so effective. And the 6pdr is a good deal behind the KwK40 in this respect, by some 5 Kilo Joules pr. cm^2.