Two questions about German guns

[warspite]

a). Is the 75L70 related to the other 75s? (75L43, 75L48)?

. Why did the Germans favor smaller caliber, longer barrel guns compared to the Russians? Was this a production issue, where it was easier to modify a factory to produce longer barrels rather than a larger caliber? Or did they do it for tactical reasons - ie, easier to aim (less height drop-off and smaller deviation due to wind)?

High-velocity guns aren't the greatest for long distances since I assume the exponential factor of wind resistance cuts their relative penetrating ability much faster than a lower velocity round.

[Bone_Vulture]

Personally, I think it was an economical issue. Since Germany was running out of tungsten fast, there was a demand for a tank gun that could penetrate all enemy armor with minimal ammunition expenses.

I do not quite know what you mean by the "exponential factor of wind resistance", though. If two tank rounds of varying caliber weigh the same amount (a longer round or different alloy) and have the same velocity, the round with the smaller caliber is likely to penetrate better. Of course, there is a certain minimum for this trend, as the round must have a certain carrying volume for the HE warhead, otherwise it's just a dead slug (not as fatal to the tank crew even when penetrating).

[EDIT]

About your first question: what exactly do you mean by "related"?

[ November 28, 2003, 02:31 PM: Message edited by: Bone_Vulture ]

[Redwolf]

The Russians always went for the higher caliber to get a better HE round, both in WW2 and in the cold war.

I think a 75mm L/48 or L/70 offers better penetration for the weight and the recoil compared to higher caliber guns. Compare Tiger and Panther guns, mounting and penetration. It is also an advantage that the ammunition is smaller if you carry a lot of AP rounds and have trouble with your resupply.

[Denwad]

75mm L/75 penetrates more armor than the 88mm L/56

MV is where it's at.

[Bone_Vulture]

Originally posted by Denwad:

75mm L/75 penetrates more armor than the 88mm L/56

MV is where it's at.

True dat. Although I might be just paranoid, but penetrating 88mm seems more lethal (the HE factor?).

[warspite]

Originally posted by Bone_Vulture:

Personally, I think it was an economical issue. Since Germany was running out of tungsten fast, there was a demand for a tank gun that could penetrate all enemy armor with minimal ammunition expenses.

I do not quite know what you mean by the "exponential factor of wind resistance", though. If two tank rounds of varying caliber weigh the same amount (a longer round or different alloy) and have the same velocity, the round with the smaller caliber is likely to penetrate better. Of course, there is a certain minimum for this trend, as the round must have a certain carrying volume for the HE warhead, otherwise it's just a dead slug (not as fatal to the tank crew even when penetrating).

[EDIT]

About your first question: what exactly do you mean by "related"?

What I mean is that the loss of energy to wind resistance increases exponentially with your speed. Take cars as an example... a Civic, let's say. A 107hp Civic with .34 wind resistance might be able to reach 110mph with perfect gearing. If you swap in an engine with 214hp and adjust gearing, that same Civic might reach 150, not 220 as the "simple math" would suggest. Ever-higher speeds are all the more difficult to achieve, since drag increases exponentially, so you might need 500hp to reach 200mph in said Civic. Ergo, for our calculations, a round travelling at velocity X will lose relatively less speed (and thus penetration ability) than a round that exits at 2X.

As for my "related" question, it means just that - are the shells and guns the same basic design, or was the 75L70 designed from scratch?

[Bone_Vulture]

Like I mentioned, the total "punch" that a round possesses is a combination of it's impact velocity, diameter and mass. Obviously there are also some secondary factors like the shape of the round, it's hardness value and impact angle.

What comes to wind resistance, the most important issue is the theoretical effective range of the gun. Is the round potent within the range that the gun can aim and hit targets on? The grogs can answer this one.

I do not know how related the guns are exactly - my best bet is that the engineers had the design of the 75L/48 model, calculated how much more strength the new gun was supposed to have, and then worked down on the old model, reinforcing the structure to handle greater combustion pressure, and so on.

[Sardaukar]

I'd comment to

Russian main concern was infantry support, thus the 122/152 assault guns etc. Even IS-2 was basicly infantry support tank. Also, Soviets were not very advanced in manufacturing high-velocity anti-armour guns until late of war, leading to compensations with use of larger caliber.

Cheers,

M.S.

[Bastables]

a) The only common part is the 7,5cm shell. The cartridge is much larger and cannot be fired out of the smaller guns. The Kw.K 42 it self shares no parts with the smaller KwK, StuK and PaK 40s. The KwK 42 is based off the failed Rheinmetall 7,5cm L/60 it self based off the PaK 44 L/46

Why did the Germans prefer the smaller bores? Simply, unlike the Soviets they had the metallurgical skill necessary to build and mass manufacture long barrels that could take the stresses from High velocity cartridges. The preference for smaller bore HV weapons extended back to 26 May 1941 when Rheinmetall was tasked to design a gun with better penetration performance than 8,8cm KwK L/56. The ban on development of squeeze bore guns due to shortages in tungsten meant a more traditional high velocity gun to arm Panzers.

Other issues (As recognised by Wa Pruf6) in favour of small-bore HV guns were smaller cartridges and smaller turret rings required to mount the weapon.

The issue of long-range drop in velocity due to smaller mass is a bit of a theoretical ceteris paribus argument. The smaller 7,5cm fired from the KwK 42 L/70 out penetrates the much larger 8,8cm L/56 round up till 2000m away because of relatively more energy applied to mass, pretty good on a battlefield where long range was considered 1000m+.

The 8,8cm L/71 outpenatrates the Soviet 12,2cm round even above 2000m. The 12,2cm round inspite of being considerably larger has only a marginal superiority to the much smaller but faster 7,5cm L/70 shell below 2000m ranges.

[ November 28, 2003, 08:29 PM: Message edited by: Bastables ]

[Redwolf]

Originally posted by Bone_Vulture:

L

What comes to wind resistance, the most important issue is the theoretical effective range of the gun. Is the round potent within the range that the gun can aim and hit targets on? The grogs can answer this one.

The original assumption is right: unless it is a very special round a larger caliber shot loses penetration with range slower then the smaller caliber.

The reason is that the wind resistence is always quadratic to the diameter and the mass is usually qubic to the diameter unless it is a projectile with an unusual length. So, as the diameter grows, the mass grows much faster than the wind resistence.

Modern penetrators are very long and small diameter anyway so it doesn't apply anymore, but it did in WW2 for pretty much all solid AP shots.

[Bastables]

Originally posted by redwolf:

Modern penetrators are very long and small diameter anyway so it doesn't apply anymore, but it did in WW2 for pretty much all solid AP shots. [/QB]

No modern penatrators fire even smaller rounds at higher velocities. The energy contined in the progectiles is so great that one would have to be looking at extreme over the horizon shots before velocity loss becomes a factor relative to a slower traveling full sized 12cm round fired from the same Gun and cartridge.

Again the excess of charge/velocity in the KwK 42 7,5cm cartridge ment that it would out pentrate the 8,8cm L/56 up to 2000m away. In a war where normal battle ranges between tanks is below 2000m, the smaller high velocity shells have the advantage.

[Mr. Tittles]

I think Panther projectiles have an extra driving band so they may not have been common to other types. But the complete fixed rounds would not be usable anyway in any other gun.

A German 1944 Panzer division would have:

1. 75L70 (Panther and JagdPanzerIVL70)

2. 75L48(PanzerIV and StuG and JagdPanzerL48)

3. 75L24(halftrack, AC and possibly PanzerIIIN)

4. 75L46 (antitank guns, towed and perhaps SP)

This means supply has to handle AP, HE and special ammo for each of these groups.

If the Panzer division had captured vehicles or Tigers, then they would also need to supply these 'groups'.

I wonder how much 'reloading' may have been going on. Supposedly, the Germans did not discard spent tank cartridges. If they reloaded, then they would need a way to insure that the brass was still good (or could be repaired/shaped), powder, caps and, of course, shells. I would guess that such a function would take place at a remote depot and not within a division.

[ November 29, 2003, 11:22 AM: Message edited by: Mr. Tittles ]

[rexford]

The Panther 75L70 fired a 6.8 kg round at 935 m/s, the PzKpfw IVH 75L48 fired the same weight round at 750 m/s.

Using a ballistic trajectory program the 1000m velocity for each round is estimated to be:

At 1000m Range

==============

75L48, 634 m/s, 84.5% of muzzle velocity, 1.45 seconds. velocity drops 116 m/s within 1000m

75L70, 803 m/s, 85.9% of muzzle velocity, 1.15 seconds, velocity drops 132 m/s within 1000m

The faster round loses a lower percentage of its initial velocity from gun to 1000m. Strange looking result at first glance.

But it really isn't that strange a result.

The velocity loss per second is proportional to the velocity squared times the drag factor, and higher velocity rounds have a smaller drag coefficient. So the Panther 75mm loses more velocity per second than the PzKpfw IVH, but less than the velocity squared term would suggest.

But, and this is the key, higher velocity rounds also travel a greater distance per second, so the bottom line is that the Panther 75mm round retains a higher percentage of its initial velocity at 1000m compared to 75L48.

The Panther 75mm trajectory is much flatter than the Pzkpfw IVH 75mm, so a Panther crew will hit more often than the PzKpfw IVH for the same range estimation error. In addition, the Panther 75mm had a much smaller constant aim random error than the 75L48, which also contributed to better accuracy.

The Tiger 88L56 had one of the smallest constant aim random errors of any WW II gun, which helped to improve on the accuracy which would obtained from a none too high 780 m/s muzzle velocity.

[ November 29, 2003, 09:24 PM: Message edited by: rexford ]

[Other Means]

OT,

are you named for HMS Warspite ? ahhh got to be my favorite ship. hard to think of a 36k ton dreadnought as having personality but that one certainly did.

fought in Jutland, where a British Cruiser was damaged & being set upon by the German High Seas fleet. Warspites steering jammed, she circled around the cruiser drawing fire while it escaped. then the the steering magically un-jammed allowing it to escape.

then fought in WWII before being sold for scrap. she wouldn't go and parted her tow lines to beach herself.

personality i tell you.

[Mr. Tittles]

Originally posted by rexford:

The Panther 75L70 fired a 6.8 kg round at 935 m/s, the PzKpfw IVH 75L48 fired the same weight round at 750 m/s.

Using a ballistic trajectory program the 1000m velocity for each round is estimated to be:

At 1000m Range

==============

75L48, 634 m/s, 84.5% of muzzle velocity, 1.45 seconds. velocity drops 116 m/s within 1000m

75L70, 803 m/s, 85.9% of muzzle velocity, 1.15 seconds, velocity drops 132 m/s within 1000m

The faster round loses a lower percentage of its initial velocity from gun to 1000m. Strange looking result at first glance.

But it really isn't that strange a result.

The velocity loss per second is proportional to the velocity squared times the drag factor, and higher velocity rounds have a smaller drag coefficient. So the Panther 75mm loses more velocity per second than the PzKpfw IVH, but less than the velocity squared term would suggest.

But, and this is the key, higher velocity rounds also travel a greater distance per second, so the bottom line is that the Panther 75mm round retains a higher percentage of its initial velocity at 1000m compared to 75L48.

When leading a moving vehicle, the Panther round would also have the edge. Its round gets there 3/10ths of a second quicker.

[Berlichtingen]

Originally posted by redwolf:

The Russians always went for the higher caliber to get a better HE round, both in WW2 and in the cold war.

The trend goes back at least to the time of Frederick the Great, and probably back to Peter the Great

[rum]

Originally posted by Sardaukar:

Russian main concern was infantry support, thus the 122/152 assault guns etc. Even IS-2 was basicly infantry support tank.

Wrong.

IS-2 was "heavy breakthrough" tank

Originally posted by Sardaukar:

Also, Soviets were not very advanced in manufacturing high-velocity anti-armour guns until late of war, leading to compensations with use of larger caliber.

Wrong.

Grabin made his ZIS-2 _before_ the war.

[rum]

Originally posted by warspite:

. Why did the Germans favor smaller caliber, longer barrel guns compared to the Russians?

Do you mean "tank cannons" or "all cannons"?

If "all cannons" then you are wrong. German infantry was using sIG-33 150mm gun. Phew... Russian infantry had only 76mm as a main arty.

[Andreas]

Originally posted by rum:

</font><blockquote>quote:</font><hr />Originally posted by Sardaukar:

Russian main concern was infantry support, thus the 122/152 assault guns etc. Even IS-2 was basicly infantry support tank.

Wrong.

IS-2 was "heavy breakthrough" tank </font>

[Bone_Vulture]

Originally posted by rum:

</font><blockquote>quote:</font><hr />Originally posted by warspite:

. Why did the Germans favor smaller caliber, longer barrel guns compared to the Russians?

Do you mean "tank cannons" or "all cannons"?

If "all cannons" then you are wrong. German infantry was using sIG-33 150mm gun. Phew... Russian infantry had only 76mm as a main arty. </font>

[Sardaukar]

Originally posted by rum:

Wrong.

IS-2 was "heavy breakthrough" tank

Wrong.

Grabin made his ZIS-2 _before_ the war.

IS-2 was *designed* to be heavy breakthrough tank. Doesn't mean it excelled in it, especially against enemy armour. What is was good at, was to keep up with T-34 and add massive HE firepower.

Grabin *designed* ZIS-2 before war, didn't make much impact 1941-42, did it...until production got geared up.

I think you are speaking intentions, and I'm speaking about practicalities. Our perceptions don't cancel each other, just that we look things from different perspective.

Cheers,

M.S.

[Kanonier Reichmann]

Originally posted by Berlichtingen:

The trend goes back at least to the time of Frederick the Great, and probably back to Peter the Great

Napoleonic times is probably a good example of this where the Russian army had 12 pounder cannons as their common artillery piece (as were the French) while the British were still using 6 pounders extensively.

Regards

Jim R.

[rum]

Originally posted by Andreas:

Rum

I always thought the role of a heavy breakthrough tank in the Soviet doctrine was to support the infantry at the point of breakthrough. Exploitation was then left to T34 or Sherman equipped formations.

Andreas, right. Perharbs i should add what under "breakthrough" i mean the attack on a fortified well-prepared enemy position, and the heavy breakthrough tanks are designed to help infantry assault such position, bustign the concrete pillboxes, mg pillboxes, and other fortifications.

IMHO the "heavy breakthrough" origins concept could be traced to the Winter War/afterwar, when the KV-2 tank was urgently built, specialy to me able to deal with fortification.

Check the memories of the "heavy artillery" officer and the difficulties he met then busting bunkers.

http://mannerheim-line.com/veterans/Leontief.htm

[rum]

Originally posted by Sardaukar:

Grabin *designed* ZIS-2 before war, didn't make much impact 1941-42, did it...until production got geared up.

I think you are speaking intentions, and I'm speaking about practicalities. Our perceptions don't cancel each other, just that we look things from different perspective.

Sardukar, ZiS-2 was made to the RKKA before the war.

http://www.battlefield.ru/guns/atg_4.html

if you look this table

http://krieg.wallst.ru/frames-h/hkanone-1.html

you'd see what above 300 were produced in 1941. The table is in russian language but you should have no trouble to see numbers like "57mm" and "1941" and "371"

If you are realy interested i could search for some real documents for the deployment of this gun during 1941.

Sorry seems i failed to understand your phrase about "intentions and practicalities", prolly language barier prevents me from .

As far as i see, ZiS-2 _was_ in action in 1941, it _was_ superior to the PAK-38 in the AP terms, and USSR _had_ the technologies to produce high-velocity cannons in the early-war and even before.

Of cause the price of this cannons was astronomics, but they did prodused and used in 1941.

[Andreas]

Originally posted by Sardaukar:

</font><blockquote>quote:</font><hr />Originally posted by rum:

Wrong.

IS-2 was "heavy breakthrough" tank

Wrong.

Grabin made his ZIS-2 _before_ the war.

IS-2 was *designed* to be heavy breakthrough tank. Doesn't mean it excelled in it, especially against enemy armour. What is was good at, was to keep up with T-34 and add massive HE firepower. </font>