I've notice that russian score is "30 degree."
Best Tank Destroyer/ self-propelled gun
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I've notice that russian score is "30 degree."
everything else being equal, The ratio of KE pr. surface is directly proportional to KE, isn't it?
5200/3107=85.49/51.09 (almost)
ratio of KE pr. surface =(925/750)^2=152%, while actual ratio is 137/99=138%, De marre's method result is 135%......So I still believe De marre when sloped plate applied.
Perhaps they didn't use de marre slope formular correctly.
BTW, the hardness is NOT direct proportional to amor quality.
1) If a amor's hardness is "too high", the toughness perhaps will be sacrificed, in the end the quality of amore may be worse!
2) 260 BHN amor's quality will probably be equal to 240 BHN amor because the projectile's hardness is far more 300 BHN, I still remember approximately it's around 500-600 even 700 BHN(17 pdr).
Tanks in World War 2 :: View topic - Gun Penetration tables
Now I am also suspecting the battlefield.ru site. BTW，I trust Tony Williams.
However, the conclusion of penetration directly proportinal to HE pr. cm^2 is still rejected by me. Since you believe the kwk43 has a penetration over 200mm vertical @ 650meters, how do you explian kwk43 can NOT penetrate panther D glacis beyond 650 meter? Is the panther D's front protection is equivalent to 200mm+ vertical? Or the ruusian site told a lie or russian kubinka test is mock! If the panther D=170mm vertical (smaller than 200mm due to D25T's big diameter), the JS2 can not penetrate panther D glacis anyway because there was no APCR shell for D25T in WWII.
I believe panther D glacis is invunlable to M3 L50 90mm gun,soviet L53 85mm and German L56 88mm, but panther G glacis will be penetrated by M3 at very close range.
That's right. M3 is L50 90mm, it's slightly better than L56 88mm because the projectile's velocity and weight is slightly greater than L56 88mm's. The kwk42's penetration is better than L56 88mm when hitting vertical or low obilique plate. However, the late version of M3 should be equal to kwk42, and T15E2 gun should be better than kwk42, T15E2 gun is equal to kwk43's penetration.
Now I am also suspecting the battlefield.ru site. BTW，I trust Tony Williams.
However, the conclusion of penetration directly proportinal to HE pr. cm^2 is still rejected by me. Since you believe the kwk43 has a penetration over 200mm vertical @ 650meters, how do you explian kwk43 can NOT penetrate panther D glacis beyond 650 meter? Is the panther D's front protection is equivalent to 200mm+ vertical? Or the ruusian site told a lie or russian kubinka test is mock! If the panther D=170mm vertical (smaller than 200mm due to D25T's big diameter), the JS2 can not penetrate panther D glacis anyway because there was no APCR shell for D25T in WWII.
I believe panther D glacis is invunlable to M3 L50 90mm gun,soviet L53 85mm and German L56 88mm, but panther G glacis will be penetrated by M3 at very close range.
That's right. M3 is L50 90mm, it's slightly better than L56 88mm because the projectile's velocity and weight is slightly greater than L56 88mm's. The kwk42's penetration is better than L56 88mm when hitting vertical or low obilique plate. However, the late version of M3 should be equal to kwk42, and T15E2 gun should be better than kwk42, T15E2 gun is equal to kwk43's penetration.
Glen,
Everything else being equal (External shape, BHN of nose body and internal core shape etc etc) penetration performance is always proportional to KE pr. surface area. Thats a basic law of physics, one which is always used when you're trying figure out the penetrative performance of a particular projectile, it is the very basis upon which any penetration calculation can be made.
Its very simple really when you think about it; For example What object requires the most energy applied to it for it to be able to penetrate your skin flesh, a needle or a soda bottle ?? I'd like you to answer that question and explain why one of these two requires less energy to do the job, when you've done that we can continue this discussion.
This will also help you realize why SABOT rounds are the primary AP arounds used for AT purposes and why the projectiles are shaped the way they are today. The very same principle of high KE pr. surface area is what the APCR APDS projectile relies on for its increased penetration peformance over the std. APCBC projectile.
Modern APFSDS-T projectile
Everything else being equal (External shape, BHN of nose body and internal core shape etc etc) penetration performance is always proportional to KE pr. surface area. Thats a basic law of physics, one which is always used when you're trying figure out the penetrative performance of a particular projectile, it is the very basis upon which any penetration calculation can be made.
Its very simple really when you think about it; For example What object requires the most energy applied to it for it to be able to penetrate your skin flesh, a needle or a soda bottle ?? I'd like you to answer that question and explain why one of these two requires less energy to do the job, when you've done that we can continue this discussion.
This will also help you realize why SABOT rounds are the primary AP arounds used for AT purposes and why the projectiles are shaped the way they are today. The very same principle of high KE pr. surface area is what the APCR APDS projectile relies on for its increased penetration peformance over the std. APCBC projectile.
Modern APFSDS-T projectile
Now you're just not making any sense glen...
Why would physics suddenly change ?
Also why is it that in actual real life testing the 8.8cm KwK43 manages to penetrate 201-202mm of the same type armor at 100m, ~1.67 times as much as the 8.8cm KwK36 manages at the same distance ? And why is it that this corresponds perfectly well with the ~1.67 times as much KE produced by the KwK43 ?
The answer is simple; Everything else being equal penetration performane is proportional to KE pr. surface area!
Why would physics suddenly change ?
Also why is it that in actual real life testing the 8.8cm KwK43 manages to penetrate 201-202mm of the same type armor at 100m, ~1.67 times as much as the 8.8cm KwK36 manages at the same distance ? And why is it that this corresponds perfectly well with the ~1.67 times as much KE produced by the KwK43 ?
The answer is simple; Everything else being equal penetration performane is proportional to KE pr. surface area!
I believe the reason is the problem of kwk43's target plate which is inferior to kwk36's, don't you remember that the Panther G's plate quality has declined from Panther D's?
I suggest you to compute kwk40 vs kwk42 in order to find whether the penetration is directly proportional to KE pr. surface area or not.
Like I said the quality of the test plate stayed completely unchanged throughout the war. The plates had to go through several quality control tests in order even to be accepted. The accepttance criteria was a BHN of 250-260, if that wasn't achieved the plates were remelded, simple as that.
And OK, lets compare the 7.5cm KwK40 with the KwK42:
7.5cm KwK42 L/70
Projectile weight: 6.8 kg (APCBC)
Sectional Density: 1.719
Muzzle Velocity: 935 m/s
Total Kinetic Energy: 2979 KJ
Kinetic Energy pr. cm^2: 67.43 KJ
7.5cm KwK40 L/48
Projectile weight: 6.8 kg (APCBC)
Sectional Density: 1.719
Muzzle Velocity: 790 m/s
Total Kinetic Energy: 2122 KJ
Kinetic Energy pr. cm^2: 48.03 KJ
67.43 / 48.03 gives a ratio of 1.40
106mm / 138mm gives a ratio of 1.30
Now this doesn't illustrate anything other than the KwK42 fired a different APCBC projectile, which it did, and the same actually goes for the KwK43 KwK36. When you add extra velocity (ei. energy) to a round you will have to change its material composition in order to be strong enough for this extra energy, either that or you risk shattering effects amongst other things upon impact. The Brinnell hardness levels of various parts of the projectile needs to be both hardened and softened, in effect making a new projectile, hence the different designation between the KwK36's Pzgr.39-1 and the KwK43's Pzgr.39/43, as-well as the KwK40's Pzgr-39-1 and the KwK42's Pzgr.39/42.
Each gun had is own APCBC projectile which was optimized for that particular guns characteristics. The difference between these rounds was the heat treatments of the various parts of the projectile and different drive band designs, the Pzgr.39/43 for example featured wider drive bands than the Pzgr.39-1 because of the much higher pressures reached in the KwK43/PaK43 barrels.
And OK, lets compare the 7.5cm KwK40 with the KwK42:
7.5cm KwK42 L/70
Projectile weight: 6.8 kg (APCBC)
Sectional Density: 1.719
Muzzle Velocity: 935 m/s
Total Kinetic Energy: 2979 KJ
Kinetic Energy pr. cm^2: 67.43 KJ
7.5cm KwK40 L/48
Projectile weight: 6.8 kg (APCBC)
Sectional Density: 1.719
Muzzle Velocity: 790 m/s
Total Kinetic Energy: 2122 KJ
Kinetic Energy pr. cm^2: 48.03 KJ
67.43 / 48.03 gives a ratio of 1.40
106mm / 138mm gives a ratio of 1.30
Now this doesn't illustrate anything other than the KwK42 fired a different APCBC projectile, which it did, and the same actually goes for the KwK43 KwK36. When you add extra velocity (ei. energy) to a round you will have to change its material composition in order to be strong enough for this extra energy, either that or you risk shattering effects amongst other things upon impact. The Brinnell hardness levels of various parts of the projectile needs to be both hardened and softened, in effect making a new projectile, hence the different designation between the KwK36's Pzgr.39-1 and the KwK43's Pzgr.39/43, as-well as the KwK40's Pzgr-39-1 and the KwK42's Pzgr.39/42.
Each gun had is own APCBC projectile which was optimized for that particular guns characteristics. The difference between these rounds was the heat treatments of the various parts of the projectile and different drive band designs, the Pzgr.39/43 for example featured wider drive bands than the Pzgr.39-1 because of the much higher pressures reached in the KwK43/PaK43 barrels.
delcyros
Tech Sergeant
CC, someone here knows the De Marre Nickel-steel armour penetration formula of 1890. There has a lot moved since then but it is very important to know it.
There are a numbers of formulas around these days, I personally prefer Nathan Okuns approach to defeat homogenious armour, even if this is optimized on low velocity impacts:
some other in the park:
A. FAIRBAIRN (ENGLISH, CIRCA 1865)
T/D = (0.0007692)[(W/D3)V2]0.5
Linear increase of T with increasing V nearly correct for thin plates at normal obliquity and/or with projectiles that suffer progressive damage that gradually reduces penetration ability as plate thickness increases (solid wrought-iron round shot, for example).
B. TRESSIDER (ENGLISH, EARLY 1870'S)
T/D = (0.00003798)(W/D3)0.5V1.5 = (0.00003798)[(W/D3)V2]0.75/(W/D3)0.25
Increase of T with V is close to average value for medium-thickness plates (0.25-0.75 caliber) at low obliquity with a non-deforming projectile. Note that the power of the weight density function is only one-third the power of the velocity, not one-half as a true total kinetic energy function would require, meaning that increasing the projectile's weight has less effect on its penetration than all other armor penetration formulae given here require. While in agreement with my data on penetrating hard, brittle armor, such as face-hardened armor, though much less extreme (see INTRODUCTION, above), this reduced dependency on projectile weight is not evident in any of my data for penetrating homogeneous, ductile armor with tapered-nose (pointed or rounded) projectiles--flat-nose projectiles punching out armor plugs may also show this reduced dependence on weight under some conditions, especially against thin plates. Perhaps the plates were acting in a brittle manner due to poor quality control (dirt and other impurities in the metal and improper crystal structures that could not move or deform freely), forming cracks at or just after initial impact, prior to the entire projectile getting involved in the impact, or perhaps many of the tests were done with flat-nosed projectiles against thin plates. Lack of a scaling term implies that these effects were for all plate thicknesses against all size projectiles more-or-less identically.
C. KRUPP WROUGHT IRON (GERMAN, EARLY 1870'S)
T/D = (0.00004643)[(W/D3)V2]0.75
Similar to Tressider Formula, but total kinetic energy is used.
D. DE MARRE WROUGHT IRON (FRENCH, LATE 1870'S)
T/D = (0.00002778)D0.1542[(W/D3)V2]0.7695
A slightly revised version of the Krupp Formula of C., above, using the total kinetic energy and having a slightly higher rate of increase in penetration with the striking velocity and/or projectile weight (possibly due to the use of more sharply pointed projectile noses or higher average plate thickness or projectiles that suffer less deformation on impact). Note also the existence of a simple scaling term of the form "Dd" that implies that larger projectiles will more easily pierce plates that are proportionately scaled up in thickness than their otherwise identical smaller scale models of both plate and projectile. Part of this is due to cracking and shearing failure, which occurs on surfaces and thus has a distinct scaling effect compared to the increase in projectile weight (and hence total kinetic energy) with increasing size, but much is probably due at the time to plate quality decreasing as thickness increased.
E. GAVRE (FRENCH, 1870'S)
T/D = (0.00002887)D0.42857[(W/D3)V2]0.71429
Similar to the De Marre Wrought Iron Formula in II.D., above, but the rate of increase in penetration with kinetic energy is slightly less (more in line with later results) and the scaling term is of the same form, but considerably higher , which possibly indicates an extreme plate quality drop with increasing thickness at the French Gavre Naval Proving Ground (N.P.G.) at the time.
F. DE MARRE NICKEL-STEEL (FRENCH, CIRCA 1890)
T/D = (0.00005021)D0.07144[(W/D3)(V/C)2Cos3(Ob)]0.71429
The variable "C" is the "De Marre Coefficient" that compares the test results for the given plate to the striking velocity required to barely completely penetrate, using the Navy Ballistic Limit definition, under the same conditions an identical Nickel-steel plate of average French 1890 quality. For example, later Chromium-Nickel-steel armors such as STS had normal-obliquity "C"-values of circa 1.2-1.25. The obliquity range Ob was usually restricted to 30o. As usually used later for other homogeneous armors, the "Cos3(Ob)" term was dropped altogether and "C" was used to define the velocity ratio alone. This formula became the "standard" used for many years from which most others were developed. If the value of "C" is properly chosen, this formula works amazingly well for impacts at a fixed low obliquity using a single constant value for "C" when non-deforming pointed projectiles are used against all kinds of homogeneous ductile iron and steel plates from about 0.1 to 0.75 caliber thick--above 0.75 caliber, the exponent for the kinetic energy term increases from 0.71429 to nearly 1.0, while below 0.1 the exponent increases actually to a value higher than 1.0. The formula was also applied to face-hardened armor penetration, but value for "C" was restricted to a narrow range of plate thicknesses, requiring a table of "C" values. Note that it has a very small, but significant, scaling term of the "Dd" form that matches homogeneous armor test results reasonably well, which is being caused by the cracking of the armor that occurs with even the best ductile homogeneous iron and steel.
and finally (and most important when considering german APC´s
G. KRUPP ALL-PURPOSE ARMOR PENETRATION (GERMAN, 1930'S)
T/D = (0.30386)D0.25[(W/D3)(V/C)2]0.625
Note that this is almost exactly the same as the U.S. Davis Harveyized Nickel-Steel Vs Capped AP Projectile, with the addition of the coefficient "C" that acts exactly the same as the De Marre Coefficient of the De Marre Nickel-Steel Formula (even the same letter "C" was used). The value of "C" varied from a minimum of 525 for most Armor-Piercing, Capped (APC) projectiles penetrating unbroken through mild steel, through 655-694 for average APC projectiles penetrating unbroken through German Krupp post-1930 "Wotan Harte" (Hardened 'Wotan' armor steel) (Wh) homogeneous (horizontal and thin vertical) armor, to a maximum of 804 for the weakest APC projectiles penetrating unbroken through KC n/A (the last, post-1930 form of Krupp's own "Krupp Cemented" armor, called "New Type") or tougher thinner plates for tanks, though the specific projectile used modifies this value considerably in most cases, sometimes, but not always, compensating for the large scaling term that does not apply to most forms of homogeneous, ductile armor and for the use of total kinetic energy for the face-hardened armor computations. See the table at the end of this entry for typical "C" values. This formula is for normal obliquity only; oblique impact was handled by a special formula/data table set produced for each projectile separately.
definitions are important.
best regards,
delc
There are a numbers of formulas around these days, I personally prefer Nathan Okuns approach to defeat homogenious armour, even if this is optimized on low velocity impacts:
some other in the park:
A. FAIRBAIRN (ENGLISH, CIRCA 1865)
T/D = (0.0007692)[(W/D3)V2]0.5
Linear increase of T with increasing V nearly correct for thin plates at normal obliquity and/or with projectiles that suffer progressive damage that gradually reduces penetration ability as plate thickness increases (solid wrought-iron round shot, for example).
B. TRESSIDER (ENGLISH, EARLY 1870'S)
T/D = (0.00003798)(W/D3)0.5V1.5 = (0.00003798)[(W/D3)V2]0.75/(W/D3)0.25
Increase of T with V is close to average value for medium-thickness plates (0.25-0.75 caliber) at low obliquity with a non-deforming projectile. Note that the power of the weight density function is only one-third the power of the velocity, not one-half as a true total kinetic energy function would require, meaning that increasing the projectile's weight has less effect on its penetration than all other armor penetration formulae given here require. While in agreement with my data on penetrating hard, brittle armor, such as face-hardened armor, though much less extreme (see INTRODUCTION, above), this reduced dependency on projectile weight is not evident in any of my data for penetrating homogeneous, ductile armor with tapered-nose (pointed or rounded) projectiles--flat-nose projectiles punching out armor plugs may also show this reduced dependence on weight under some conditions, especially against thin plates. Perhaps the plates were acting in a brittle manner due to poor quality control (dirt and other impurities in the metal and improper crystal structures that could not move or deform freely), forming cracks at or just after initial impact, prior to the entire projectile getting involved in the impact, or perhaps many of the tests were done with flat-nosed projectiles against thin plates. Lack of a scaling term implies that these effects were for all plate thicknesses against all size projectiles more-or-less identically.
C. KRUPP WROUGHT IRON (GERMAN, EARLY 1870'S)
T/D = (0.00004643)[(W/D3)V2]0.75
Similar to Tressider Formula, but total kinetic energy is used.
D. DE MARRE WROUGHT IRON (FRENCH, LATE 1870'S)
T/D = (0.00002778)D0.1542[(W/D3)V2]0.7695
A slightly revised version of the Krupp Formula of C., above, using the total kinetic energy and having a slightly higher rate of increase in penetration with the striking velocity and/or projectile weight (possibly due to the use of more sharply pointed projectile noses or higher average plate thickness or projectiles that suffer less deformation on impact). Note also the existence of a simple scaling term of the form "Dd" that implies that larger projectiles will more easily pierce plates that are proportionately scaled up in thickness than their otherwise identical smaller scale models of both plate and projectile. Part of this is due to cracking and shearing failure, which occurs on surfaces and thus has a distinct scaling effect compared to the increase in projectile weight (and hence total kinetic energy) with increasing size, but much is probably due at the time to plate quality decreasing as thickness increased.
E. GAVRE (FRENCH, 1870'S)
T/D = (0.00002887)D0.42857[(W/D3)V2]0.71429
Similar to the De Marre Wrought Iron Formula in II.D., above, but the rate of increase in penetration with kinetic energy is slightly less (more in line with later results) and the scaling term is of the same form, but considerably higher , which possibly indicates an extreme plate quality drop with increasing thickness at the French Gavre Naval Proving Ground (N.P.G.) at the time.
F. DE MARRE NICKEL-STEEL (FRENCH, CIRCA 1890)
T/D = (0.00005021)D0.07144[(W/D3)(V/C)2Cos3(Ob)]0.71429
The variable "C" is the "De Marre Coefficient" that compares the test results for the given plate to the striking velocity required to barely completely penetrate, using the Navy Ballistic Limit definition, under the same conditions an identical Nickel-steel plate of average French 1890 quality. For example, later Chromium-Nickel-steel armors such as STS had normal-obliquity "C"-values of circa 1.2-1.25. The obliquity range Ob was usually restricted to 30o. As usually used later for other homogeneous armors, the "Cos3(Ob)" term was dropped altogether and "C" was used to define the velocity ratio alone. This formula became the "standard" used for many years from which most others were developed. If the value of "C" is properly chosen, this formula works amazingly well for impacts at a fixed low obliquity using a single constant value for "C" when non-deforming pointed projectiles are used against all kinds of homogeneous ductile iron and steel plates from about 0.1 to 0.75 caliber thick--above 0.75 caliber, the exponent for the kinetic energy term increases from 0.71429 to nearly 1.0, while below 0.1 the exponent increases actually to a value higher than 1.0. The formula was also applied to face-hardened armor penetration, but value for "C" was restricted to a narrow range of plate thicknesses, requiring a table of "C" values. Note that it has a very small, but significant, scaling term of the "Dd" form that matches homogeneous armor test results reasonably well, which is being caused by the cracking of the armor that occurs with even the best ductile homogeneous iron and steel.
and finally (and most important when considering german APC´s
G. KRUPP ALL-PURPOSE ARMOR PENETRATION (GERMAN, 1930'S)
T/D = (0.30386)D0.25[(W/D3)(V/C)2]0.625
Note that this is almost exactly the same as the U.S. Davis Harveyized Nickel-Steel Vs Capped AP Projectile, with the addition of the coefficient "C" that acts exactly the same as the De Marre Coefficient of the De Marre Nickel-Steel Formula (even the same letter "C" was used). The value of "C" varied from a minimum of 525 for most Armor-Piercing, Capped (APC) projectiles penetrating unbroken through mild steel, through 655-694 for average APC projectiles penetrating unbroken through German Krupp post-1930 "Wotan Harte" (Hardened 'Wotan' armor steel) (Wh) homogeneous (horizontal and thin vertical) armor, to a maximum of 804 for the weakest APC projectiles penetrating unbroken through KC n/A (the last, post-1930 form of Krupp's own "Krupp Cemented" armor, called "New Type") or tougher thinner plates for tanks, though the specific projectile used modifies this value considerably in most cases, sometimes, but not always, compensating for the large scaling term that does not apply to most forms of homogeneous, ductile armor and for the use of total kinetic energy for the face-hardened armor computations. See the table at the end of this entry for typical "C" values. This formula is for normal obliquity only; oblique impact was handled by a special formula/data table set produced for each projectile separately.
definitions are important.
best regards,
delc
delcyros
Tech Sergeant
I believe it is unjustified to theoretically calculate penetration performances.Prooving ground tests should be the primary source. As Glen has pointed out above, quality differences in plates, caps, projectile bodies and other factors attribute for a wide range of differences in penetrations and one should be careful to study the plate acceptance limits in the first place. Furtherly, the De Marre Nickel steel formula used here is not very good used in the role for comparsion of ww2 projectiles. It was developed in order to get preliminary estimations of the performances of solid AP-shots (APCBC was not invented by the 1870´s) against a large number of armour plates with a thickness / diameter relation of in between 0.1 and 0.75 (= 8.8mm to 66 mm plate thickness in our case).
The program I use for theoretical penetration calculations does not account for the special properties of the PzGr.39/42 but may return good results of a projectile with basic identic properties in weight and size but different properties in shape (it´s semi pointed, in the middle of in between blunt shaped and very pointed) but without AP-cap. AP-caps as the one in question do slightly enhance the penetration performance at high obliquity impact conditions due to the sombrero shaped shoulder (better normalization prior to shattering), while not detracting from vertical impact condition (cap shatters, revealing the pointed AP-body).
Also keep in mind that thinner plates such as used on the Panther slopes were treated more carefully in production than thicker plates and generally offer more *relative stopping power due to higher hardness while still beeing ductile. Applying any formula here is tricky to say at least, cause You would come in the uncomfortable situation that your basic assumption would be that the effective stopping power euqitations of the thick and thin plates are identic, the difference is beeing defined by thickness alone, which by any means are not!
best regards,
delc
The program I use for theoretical penetration calculations does not account for the special properties of the PzGr.39/42 but may return good results of a projectile with basic identic properties in weight and size but different properties in shape (it´s semi pointed, in the middle of in between blunt shaped and very pointed) but without AP-cap. AP-caps as the one in question do slightly enhance the penetration performance at high obliquity impact conditions due to the sombrero shaped shoulder (better normalization prior to shattering), while not detracting from vertical impact condition (cap shatters, revealing the pointed AP-body).
Also keep in mind that thinner plates such as used on the Panther slopes were treated more carefully in production than thicker plates and generally offer more *relative stopping power due to higher hardness while still beeing ductile. Applying any formula here is tricky to say at least, cause You would come in the uncomfortable situation that your basic assumption would be that the effective stopping power euqitations of the thick and thin plates are identic, the difference is beeing defined by thickness alone, which by any means are not!
best regards,
delc
Very true, however it is worth remembering that German test plates had to meet strickt criteria in order to even be accepted.
But let us assume all guns fired the same shape design projectile of good quality, what would the penetration performance be between the guns ? Now we're just looking at the capability of each gun, not actual performance.
But let us assume all guns fired the same shape design projectile of good quality, what would the penetration performance be between the guns ? Now we're just looking at the capability of each gun, not actual performance.
delcyros
Tech Sergeant
The prooving ground trials conducted at Meppen 1943 with 10.2 Kg APCBC PzGr. 39-3 fired from KWK42 at 1000m/s mv are consistent with the prooving ground trials conducted with Flak 41 firing 10.2Kg APCBC Pz.Gr. 39-3 at 980 m/s velocity. The former showed a penetration of 201-203mm, the latter Flak showed a penetration of 197mm (both at 100m, the obliquity condition is unknown, we cannot be sure that it means 30 deg.!!!), which is in the right ballpark of what we would expect according to the difference in mv. It does also match nicely US prooving ground tests which gave a penetration of 7.87" US homogenious at vertical and 1000 yards for the 88mmL71.
The 120mm armour plate tested for the KWK 36 was manufactured according to specifications calling for a BRH of 279-307 Brinell (Specification PP793 and PP7182 for thicknesses of 85mm to 120mm, date unknown. The two specifications were slightly different alloys but had the same BHN). It was of very tough quality compared to the 200mm armour plate of the latter tests
which was manufactured according to a specification (E43 is a bit on the late side but there was a preceeding specification calling for the same BHN) requiring a BRH of 220-265.
The 120mm armour plate tested for the KWK 36 was manufactured according to specifications calling for a BRH of 279-307 Brinell (Specification PP793 and PP7182 for thicknesses of 85mm to 120mm, date unknown. The two specifications were slightly different alloys but had the same BHN). It was of very tough quality compared to the 200mm armour plate of the latter tests
which was manufactured according to a specification (E43 is a bit on the late side but there was a preceeding specification calling for the same BHN) requiring a BRH of 220-265.
According to Thomas L. Jentz all German trials were conducted against 30 degree sloped plates, including all those with the KwK43 PaK43, this was std. practice.
The BHN levels of 279 - 307 surprise me, but regardless such a high BHN isn't as effective against super high velocity projectiles (KwK43) as armor of 265 BHN. The most effective armour has BHN levels around 255 - 265 BHN.
The BHN levels of 279 - 307 surprise me, but regardless such a high BHN isn't as effective against super high velocity projectiles (KwK43) as armor of 265 BHN. The most effective armour has BHN levels around 255 - 265 BHN.
delcyros
Tech Sergeant
I just give only what I have seen so far. The obliquity condition is never mentioned in the german avaiable primary sources.
There is nothing like a most effective BHN level for armour plates. The higher, the more stopping power it has. Diminishing returns for overhard plates exist in manufacturing constraints and britellness (esspeccially hydrogen embrittelment and cast armour) and the ductility against large calibre impacts (large starts with 8" and more), the latter hardly beeing a factor against tank guns.
A 200mm, 260 BHN plate has less stopping power than a 120mm BHN 300 scaled up to 200mm thickness of the same quality, if it would be possible to treat such a plate without quality loss wrt laminations and ductility, which is the limiting factor. Otherwise they would have produced them.
There is nothing like a most effective BHN level for armour plates. The higher, the more stopping power it has. Diminishing returns for overhard plates exist in manufacturing constraints and britellness (esspeccially hydrogen embrittelment and cast armour) and the ductility against large calibre impacts (large starts with 8" and more), the latter hardly beeing a factor against tank guns.
A 200mm, 260 BHN plate has less stopping power than a 120mm BHN 300 scaled up to 200mm thickness of the same quality, if it would be possible to treat such a plate without quality loss wrt laminations and ductility, which is the limiting factor. Otherwise they would have produced them.
ratio of KE=140%
ratio of actual penetration=130%
ratio of de marre=127%
De Marre's theory is more accurate.
Other examples:
De Marre's theory is more accurate.
De Marre's theory is more accurate.
De Marre's theory is more accurate.
You can compute more by yourself from this link:
World War II Tanks - Germany's Penetration Tables
Almost every German gun obeys De Marre's theory except for Kwk43, according to Russian and American test/ battle field performance, the kwk43's official score is quite strange....probably the reason is that German could NOT produce >150mm plate whose quality is as good as thiner ones, neither could Amrican or british or Russian. The thicker the plate is ,the more difficult to retain high quality.
delcyros
Tech Sergeant
Glen, the De-Marre formula assumes solid AP-shots without cap for a very narrow range of T/D ratios and obliquities. Outside this envelope, the De-Marre formula shows results which some times work, sometimes don´t work, just like a monte carlo alike probability step system. You don´t want this condition to apply for Your question.
I fully agree in plate thickness and quality related issues. However, it could defeat 200mm plates. It´s true that 200mm are not "true" 200mm in stopping power but the 200mm it could defeat where usually of the same quality as those encountered in the battlefield. So the difference is of more theoretical interest, as it shows marked problems in calculations when applying the De-Marre formula. Never use it at T/D ratios above 1.0, differences may be fractions, but fractions are important.
When calibrating on 2420 fps striking velocity at 100m and 30 deg for the KWK 36, and assuming the projectile is with regards of it´s properties like a stand. US M79 AP, without cap and filler, the critical plate thickness at which it achieves full penetration is 4.7" at a relative quality of 1.25.
Comparing to a striking velocity of 3140 fps for the L71, I get a penetration of 7.2" single plate aequivalent of quality= 1.25 or 7.88" single plate aequivalent perforation of quality = 1.14.
BHN value for quality 1.25 = 280, matching requirements for 120mm plates
BHN value for quality 1.14 = 255, matching requirements for 200mm plates
Calculations performed with M79APCLC
best regards,
delc
I see no conflicting datas.
I fully agree in plate thickness and quality related issues. However, it could defeat 200mm plates. It´s true that 200mm are not "true" 200mm in stopping power but the 200mm it could defeat where usually of the same quality as those encountered in the battlefield. So the difference is of more theoretical interest, as it shows marked problems in calculations when applying the De-Marre formula. Never use it at T/D ratios above 1.0, differences may be fractions, but fractions are important.
When calibrating on 2420 fps striking velocity at 100m and 30 deg for the KWK 36, and assuming the projectile is with regards of it´s properties like a stand. US M79 AP, without cap and filler, the critical plate thickness at which it achieves full penetration is 4.7" at a relative quality of 1.25.
Comparing to a striking velocity of 3140 fps for the L71, I get a penetration of 7.2" single plate aequivalent of quality= 1.25 or 7.88" single plate aequivalent perforation of quality = 1.14.
BHN value for quality 1.25 = 280, matching requirements for 120mm plates
BHN value for quality 1.14 = 255, matching requirements for 200mm plates
Calculations performed with M79APCLC
best regards,
delc
I see no conflicting datas.
