Civettone
Tech Sergeant
That's right. The KaJaPa mainly fired HEAT and HESH, MV not mattering much.
As such, it was only reasonable they replaced the gun by TOW missiles.
Kris
German 75mm v Allied 75mm
- Thread starter vinnye
- Start date
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As such, it was only reasonable they replaced the gun by TOW missiles.
Kris
I think the biggest obstacle to US tank guns was that America really didnt get serious about building effective tank guns until 1940. The Germans and Soviets had a lot of experience in the Spanish Civil War and were continually upgrading weapons and chassis. The Sherman's first fight wasnt operated by the USA, but the British in North Africa, and at that time was considered a match for the MKIII and early MKIVs. The Sherman never was a good infantry support tank with respect to its armor-too thin, and it was expected that a true infantry support tank would need enough armor to survive the German anti tank defenses.
In truth, infantry support wasnt thought much of and our doctine was to have the infantry and artillery make a breakthrough so that armor would exploit it. Automotively, the Sherman was far superior to the MKV Panther but didnt have the power to penetrate the glacis. Our initial doctrine was based on the blitzcrieg tactics of the Germans, who changed their own thoughts after running into the Soviets. Our intial anti tank weapon was the 37MM based on the German model from the Spanish war. By the time we fielded our own 37, the Germans had moved onto the 57MM and then 75MM guns. The US was always behind in armor during the war. Good tactics, which included hitting the Panzer supply lines is what brought the German armor down.
In truth, infantry support wasnt thought much of and our doctine was to have the infantry and artillery make a breakthrough so that armor would exploit it. Automotively, the Sherman was far superior to the MKV Panther but didnt have the power to penetrate the glacis. Our initial doctrine was based on the blitzcrieg tactics of the Germans, who changed their own thoughts after running into the Soviets. Our intial anti tank weapon was the 37MM based on the German model from the Spanish war. By the time we fielded our own 37, the Germans had moved onto the 57MM and then 75MM guns. The US was always behind in armor during the war. Good tactics, which included hitting the Panzer supply lines is what brought the German armor down.
Shortround6
Lieutenant General
Most people adapted other guns or ammunition to tanks.
The US had the 37mm AT gun and tank gun using same ammo.
the First 75mm used in the Grant used the ammo of the French 75mm field gun of 1897. Maybe loaded just a bit hotter.
The long 75mm barreled guns used late Grants and production Shermans used the same ammo in a 9 caliber longer barrel for a modest increase in velocity.
The 3in gun in the M 10 tank destroyer was adopted from an old AA gun.
The 76mm gun used in Shermans and M-18s used the same projectiles as the 3 in gun in a lighter barrel (same length for all purposes) in a smaller cartridge case operating at higher pressures ( The science of making gun barrels had advanced from 1918 to 1941/42).
The 90mm gun used in the M-36 TD and M-26 rank was adopted from an AA gun and the experimental 105mm and 120mm guns were also adaptations of AA guns.
The US had leap frogged a number of other nations with the Sherman.
From Wiki
" Detailed design characteristics for the M4 were submitted by the Ordnance Department on 31 August 1940, but development of a prototype had to be delayed while the final production designs of the M3 were finished and the M3 entered full-scale production. On 18 April 1941, the U.S. Armored Force Board chose the simplest of five designs. Known as the T6, the design was a modified M3 hull and chassis, carrying a newly designed turret mounting the Lee's 75 mm gun. This became the Sherman."
The M3 was always a stop gap.
wiki;
"The T6 prototype was completed 2 September 1941. Unlike later M4s, the hull was cast and had a side hatch, which was eliminated from production models. The T6 was standardized as the M4 and production began in October."
Please note that this was about one year before the tank saw action with the British.
Unfortunately the US then did not keep up the pace and got side tracked with the the tank destroyer "doctrine".
The US had the 37mm AT gun and tank gun using same ammo.
the First 75mm used in the Grant used the ammo of the French 75mm field gun of 1897. Maybe loaded just a bit hotter.
The long 75mm barreled guns used late Grants and production Shermans used the same ammo in a 9 caliber longer barrel for a modest increase in velocity.
The 3in gun in the M 10 tank destroyer was adopted from an old AA gun.
The 76mm gun used in Shermans and M-18s used the same projectiles as the 3 in gun in a lighter barrel (same length for all purposes) in a smaller cartridge case operating at higher pressures ( The science of making gun barrels had advanced from 1918 to 1941/42).
The 90mm gun used in the M-36 TD and M-26 rank was adopted from an AA gun and the experimental 105mm and 120mm guns were also adaptations of AA guns.
The US had leap frogged a number of other nations with the Sherman.
From Wiki
" Detailed design characteristics for the M4 were submitted by the Ordnance Department on 31 August 1940, but development of a prototype had to be delayed while the final production designs of the M3 were finished and the M3 entered full-scale production. On 18 April 1941, the U.S. Armored Force Board chose the simplest of five designs. Known as the T6, the design was a modified M3 hull and chassis, carrying a newly designed turret mounting the Lee's 75 mm gun. This became the Sherman."
The M3 was always a stop gap.
wiki;
"The T6 prototype was completed 2 September 1941. Unlike later M4s, the hull was cast and had a side hatch, which was eliminated from production models. The T6 was standardized as the M4 and production began in October."
Please note that this was about one year before the tank saw action with the British.
Unfortunately the US then did not keep up the pace and got side tracked with the the tank destroyer "doctrine".
Good points shortround....at the time of the M3, the only tank production line was at Rock Island and they were capable of making a few hundred tanks per year, and the American's werent even sure how big a turret ring needed to be in order to handle the 75MM gun. Thats why the sponson mount for the 75 and the 37 in the turret. The powder charge on the 75 MM gun is less than half of the German 75 or 17 Pounder British. I think the Brits were on the right track with their sabot round but the science was not well understood and it did not have the needed accuracy. HESH rounds were not all they could have been mostly because of the mechanical fuzes used at that time....the piezo electric fuze really helped the performance but that came after the war.
I did read a bit on the 90MM turret from the M36 being dropped into a Sherman chassis, which gave them a more effective main gun, but even less armor on the turret and open topped to boot.
I also see that some commanders balked at upgunning to the 76MM because its HE round was much less effective than the one used for the 75, and in a way one cant blame them. There was a lot less tank to tank battles on the western side than what the Soviets had to deal with. Terrain had a lot to do with that I suspect. Taking out an antitank position with solid shot is not nearly as effective as with HE and the Shermans dealt with a lot more of that than battling another tank. The big exception in the west was the British fight at Caan.
I did read a bit on the 90MM turret from the M36 being dropped into a Sherman chassis, which gave them a more effective main gun, but even less armor on the turret and open topped to boot.
I also see that some commanders balked at upgunning to the 76MM because its HE round was much less effective than the one used for the 75, and in a way one cant blame them. There was a lot less tank to tank battles on the western side than what the Soviets had to deal with. Terrain had a lot to do with that I suspect. Taking out an antitank position with solid shot is not nearly as effective as with HE and the Shermans dealt with a lot more of that than battling another tank. The big exception in the west was the British fight at Caan.
The charge on the German 75mm/L48 round was reduced at some point after it was in service because the casing ejection jammed. At some later point the charge of the German 75mm/L46 round was also reduced a bit. I'm not sure why this was done. Maybe to keep it's performace near that of the /L48?
MacArther
Staff Sergeant
One thing that explains the discrepancy between the German and Allied 75mm was at least on the part of the Americans the focus on the Tank Destroyer Doctrine. In this line of thinking, the Sherman would support the infantry, help with the breakthrough, and NOT engage enemy tanks! The enemy tanks were to be engaged by the M6, the M3/A1 gun motor carriages, and later the much improved M10, M18, and M36. Interestingly enough, when in their element and even out of it, the motorized anti-tank groups the Americans fielded did very well for themselves and their surrounding units!
Look up"The Tank Killers: A History of America's World War II Tank Destroyer Force," it has a good deal on the doctrinal ideas, as well as accounts for how the units fought at the front, and were eventually used as stand in tanks.
Look up"The Tank Killers: A History of America's World War II Tank Destroyer Force," it has a good deal on the doctrinal ideas, as well as accounts for how the units fought at the front, and were eventually used as stand in tanks.
delcyros
Tech Sergeant
Armour in this period for tanks was homogenious rolled or cast armour. In some cases, units may employ some kind of improvisional face hardening applied as a thin, roughly 1.2" thick area on the plate´s face ("Einsatzhärtung") in order to obtain a higher hardening.
The preferred type of attack was a solid, uncapped AP-shot (no filler, just a tracer) in the US case and an APC (later APCBC) with small burster charge ("Zerleger") and base fuse element in the german case. Undenieable, the german projectile was more complex and labour intensive to mass produce.
Uncapped AP is quite good in defeating homogenious armour (requiring slightly less velocity than capped AP), provided it can remain in unbroken and unshattered condition. Beeing a solid AP-shot helps the M79 projectile here. The difference is not large but noticable, tehre is a correlation between the weight of the cap and teh striking velocity. A 15% cap requires 15% more velocity to penetrate a given plate at normal impact, while a 10% cap increases the velocity only by about 10% (US 3" and 6" AP/APC trials communicated by Dr. Allan Hershey in a paper called "The Cap effect and the Hood effect on penetration" or something like that)
However, with ever increasing impact velocities and/or impact obliquities, various forms of projectile damage may set in on uncapped projectiles. Nose shatter and breakage, deformation and compression (which a well designed projectile can limit) can be prevented by adding an armour-peircing cap, but base damage at high obliquity is more difficult to prevent. All these damages change the capabilities of the projectile to penetrate a given plate. Some changes actually may improve perforation (nose damage at high impact obliquity tends to prevent ricochet, for example, even though it would be a rare event), but any damage which is strong enough to change the perforation capabilities usually goes along with rendering the projectiles burster charge ineffective. This is a concern for the german 75mm AP as it was required to have at least some explosive effect within the target.
Initially, the german 75mm AP would start to suffer breakage when striking 100mm homogenious armour at normal (1.33 cal/plate for this projectile). This compares unfavourably with the 3"M79 AP, in whiches case 5.14" rolled homogenious armour or 1.71 cal/plate (STS) were required to damage the projectile.
The germans then tried various forms of AP-caps, triggering dramatic improvements in their AP-performances. Higher striking velocities could be exploited now, which were previously unobtainable without risking full shatter of the projectile. I have seen a set of trials with 75mm APC penetrating a 200mm homogenious armour plate at 30 deg obliquity (2.67 cal/plate!) with neither nose nor body or base damage to any of these 75mm projectiles. One of which was stopped by the plate and another just penetrated with a third even stuck in the plate at striking velocities of in between 1030 and 1070 m/s.
At 30 deg obliquity, the 3"M79 would suffer breakage starting with 0.86cal/plate thickness (65mm for the 3"M79). The projectile could still completely penetrate -even thicker plates at this obliquity- but in completely shattered or badly broken up condition. It would also require more velocity than for an intact projectile (except at very high obliquities) and specially designed HVAP could exploit this to their benefit and attain better perforation figures. This explains, I hope, why the allies didn´t opted for higher velocity of their 75mm and 3" AP-shells with correspondingly smaller propellant charges. Higher striking velocities would have been possible and entirely feasable but AP-performance of uncapped AP wouldn´t have been much improved due to the soon developing shatter-gap.
Of course one has to keep in mind to compare apples with apples. The specification for hardness changed with the thickness of the armour plate. It´s possible to cross-calibrate the performance of the 75mm using a couple of data:
[1] Lilienthalbericht 166, p.110 for german penetration data -originally classified research paper detailing developments to 1943 in german AP ammunition -differentiating plate toughness
[2] british trials with german 75mm as well as US and soviet 76mm AP/APCBC
[3] US trials with US 3" AP and german 75mm APCBC
according to these trials the british reports attributed the 75mm APCBC at 610m/s and normal impact with a penetration of 102mm. The corresponding figures from the Lilienthal file is only 90mm at this velocity. The latter beeing obtained against a plate of 147000 PSI UTS, suggesting that the british trials were executed at somehow softer armour plating (~130000 PSI UTS would yield the same penetrative result). The US trial gave apenetration of 190mm at 0 deg and 935m/s velocity -the corresponding figure of the Lilienthalreport was 186mm, obtained against a softer plate with 111000 PSI UTS.
Thicker plates had to be softer in order to avoid excessive brittelness under impact of the plate. The softer the plate, the better also the quality of the plate to perforation (less breakage) but the smaller the resistence to impact. However, once brittel breakage occured, the resistence of the plate dropped down by a considerable amount. The data of german and US trials suggest that the US trial plate was again softer than the german one, at around 108000 PSI.
Calibrated on a legend 115000 PSI plate (which is assumed to never fail by breakage- a theoretical vehicel for comparison purposes, as such plates wouldn´t be good at all thicknesses and outright poor in some), the corresponding adjusted figures for these guns would be:
at 610m/s:
75mm Pgr.39 --- 115mm penetration
3" M79 AP --- 102mm penetration
SU 76mm APC:-- 85mm penetration
-----
at 935m/s:
75mm Pgr.39 --- 179mm penetration
The 3" M79 AP could be expected to about penetrate 160mm -theoeretically at 935m/s- but instead it will undergo full shatter striking any plate thicker than 130mm. US trials to investigate the problem showed that at about 635m/s impact velocity, shatter started to occur on this projectile with 5.14" STS armour, the shatter velocity beeing dependent on thickness and obliquity, too. Capped APCBC of this projectile, and HVAP introduced late 1944 were capable to match and exceed these data but only if a sufficiently high hardness of the cap and projectile nose was choosen. As a rule of thumb, it had to match or preferably exceed the hardness of the armour engaged.
If the nose was not hard enough -and shatter occurred- things can get complicated. At normal impact, the change from a pointed nose to a shattered is associated with a roughly 1/3 increase in required striking velocity to penetrate despite shatter (the fragments have enough velocity to smash completely through the plate) but this changes with increasing obliquity and gradually gets smaller.
Theoretically, it may happen that that a given projectile penetrates at 0 to 150 yards (penetration despite shatter by excess velocity), then fails to penetrate at 150 to 800 yards (shatter), then penetrates again at 800 to 1000 yard (penetration without shatter occuring) before failing completely.
The preferred type of attack was a solid, uncapped AP-shot (no filler, just a tracer) in the US case and an APC (later APCBC) with small burster charge ("Zerleger") and base fuse element in the german case. Undenieable, the german projectile was more complex and labour intensive to mass produce.
Uncapped AP is quite good in defeating homogenious armour (requiring slightly less velocity than capped AP), provided it can remain in unbroken and unshattered condition. Beeing a solid AP-shot helps the M79 projectile here. The difference is not large but noticable, tehre is a correlation between the weight of the cap and teh striking velocity. A 15% cap requires 15% more velocity to penetrate a given plate at normal impact, while a 10% cap increases the velocity only by about 10% (US 3" and 6" AP/APC trials communicated by Dr. Allan Hershey in a paper called "The Cap effect and the Hood effect on penetration" or something like that)
However, with ever increasing impact velocities and/or impact obliquities, various forms of projectile damage may set in on uncapped projectiles. Nose shatter and breakage, deformation and compression (which a well designed projectile can limit) can be prevented by adding an armour-peircing cap, but base damage at high obliquity is more difficult to prevent. All these damages change the capabilities of the projectile to penetrate a given plate. Some changes actually may improve perforation (nose damage at high impact obliquity tends to prevent ricochet, for example, even though it would be a rare event), but any damage which is strong enough to change the perforation capabilities usually goes along with rendering the projectiles burster charge ineffective. This is a concern for the german 75mm AP as it was required to have at least some explosive effect within the target.
Initially, the german 75mm AP would start to suffer breakage when striking 100mm homogenious armour at normal (1.33 cal/plate for this projectile). This compares unfavourably with the 3"M79 AP, in whiches case 5.14" rolled homogenious armour or 1.71 cal/plate (STS) were required to damage the projectile.
The germans then tried various forms of AP-caps, triggering dramatic improvements in their AP-performances. Higher striking velocities could be exploited now, which were previously unobtainable without risking full shatter of the projectile. I have seen a set of trials with 75mm APC penetrating a 200mm homogenious armour plate at 30 deg obliquity (2.67 cal/plate!) with neither nose nor body or base damage to any of these 75mm projectiles. One of which was stopped by the plate and another just penetrated with a third even stuck in the plate at striking velocities of in between 1030 and 1070 m/s.
At 30 deg obliquity, the 3"M79 would suffer breakage starting with 0.86cal/plate thickness (65mm for the 3"M79). The projectile could still completely penetrate -even thicker plates at this obliquity- but in completely shattered or badly broken up condition. It would also require more velocity than for an intact projectile (except at very high obliquities) and specially designed HVAP could exploit this to their benefit and attain better perforation figures. This explains, I hope, why the allies didn´t opted for higher velocity of their 75mm and 3" AP-shells with correspondingly smaller propellant charges. Higher striking velocities would have been possible and entirely feasable but AP-performance of uncapped AP wouldn´t have been much improved due to the soon developing shatter-gap.
Of course one has to keep in mind to compare apples with apples. The specification for hardness changed with the thickness of the armour plate. It´s possible to cross-calibrate the performance of the 75mm using a couple of data:
[1] Lilienthalbericht 166, p.110 for german penetration data -originally classified research paper detailing developments to 1943 in german AP ammunition -differentiating plate toughness
[2] british trials with german 75mm as well as US and soviet 76mm AP/APCBC
[3] US trials with US 3" AP and german 75mm APCBC
according to these trials the british reports attributed the 75mm APCBC at 610m/s and normal impact with a penetration of 102mm. The corresponding figures from the Lilienthal file is only 90mm at this velocity. The latter beeing obtained against a plate of 147000 PSI UTS, suggesting that the british trials were executed at somehow softer armour plating (~130000 PSI UTS would yield the same penetrative result). The US trial gave apenetration of 190mm at 0 deg and 935m/s velocity -the corresponding figure of the Lilienthalreport was 186mm, obtained against a softer plate with 111000 PSI UTS.
Thicker plates had to be softer in order to avoid excessive brittelness under impact of the plate. The softer the plate, the better also the quality of the plate to perforation (less breakage) but the smaller the resistence to impact. However, once brittel breakage occured, the resistence of the plate dropped down by a considerable amount. The data of german and US trials suggest that the US trial plate was again softer than the german one, at around 108000 PSI.
Calibrated on a legend 115000 PSI plate (which is assumed to never fail by breakage- a theoretical vehicel for comparison purposes, as such plates wouldn´t be good at all thicknesses and outright poor in some), the corresponding adjusted figures for these guns would be:
at 610m/s:
75mm Pgr.39 --- 115mm penetration
3" M79 AP --- 102mm penetration
SU 76mm APC:-- 85mm penetration
-----
at 935m/s:
75mm Pgr.39 --- 179mm penetration
The 3" M79 AP could be expected to about penetrate 160mm -theoeretically at 935m/s- but instead it will undergo full shatter striking any plate thicker than 130mm. US trials to investigate the problem showed that at about 635m/s impact velocity, shatter started to occur on this projectile with 5.14" STS armour, the shatter velocity beeing dependent on thickness and obliquity, too. Capped APCBC of this projectile, and HVAP introduced late 1944 were capable to match and exceed these data but only if a sufficiently high hardness of the cap and projectile nose was choosen. As a rule of thumb, it had to match or preferably exceed the hardness of the armour engaged.
If the nose was not hard enough -and shatter occurred- things can get complicated. At normal impact, the change from a pointed nose to a shattered is associated with a roughly 1/3 increase in required striking velocity to penetrate despite shatter (the fragments have enough velocity to smash completely through the plate) but this changes with increasing obliquity and gradually gets smaller.
Theoretically, it may happen that that a given projectile penetrates at 0 to 150 yards (penetration despite shatter by excess velocity), then fails to penetrate at 150 to 800 yards (shatter), then penetrates again at 800 to 1000 yard (penetration without shatter occuring) before failing completely.
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Do you have the actual test results for these numbers or did you derive them from some sort of engineering formula? Real tests don't seem to agree. For example the US Aberdeen data Pak40 Pgr.39 ~635m/s @ 1500yds penetration=109mm.
At around 1575-1600m it gets to 610m/s where the penetration would be 104mm.
Then there's the US ballistic test of M79 in Handbook-of-Ballistic-and-Engineering-Data-for-Ammunition-Volume-2-USA-1950 stating that the Naval ballistic limit of 1911 f/s is 4". So 582 m/s is 102mm. At 610m/s the M79 would do about 107mm penetration (provided constant slope).
US tests were done vs. 230-250 BHN armor.
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delcyros
Tech Sergeant
As mentioned previously, the penetration data I referred to are ESP figures. Thus, it´s theoretical performance based upon a calibrated steel armour plate (homogenious) with 115,000 PSI tensile strength. Equivalent Steel Penetration. This way, it´s possible to compare the data from different trials using different plate properties.
Note that penetration is usually based upon interpolation of multiple shots under similar condition. You get a scatter of individual penetration events and try to lay a best fit curve through the cloud. I have the M79 "clouds" and now that a certain scatter of data realistically has to be reckoned with. The typical form to determine the grenz penetration (100% of the projectile through the plate, broken or not and completely depleting it´s energy) was:
850ms---840ms---830ms---820ms--
--+--+--+--+--+--()--+--()--(o)--(o)
where
+ is complete penetration
() is stuck in plate
(o) no penetration
-in this case the limit of perforation would be considered ~838m/s to 830m/s
The effect of tensile strength (correlated with BHN hardness as long as ductile under impact) is most significant for normal impact (0 deg in british, 90 deg in german definition) but reduces with obliquity. As an example, trials conducted 1942 with 2cm model shots (Ss and SK) on 50kg/mm^2, 100kg/mm^2 and 150kg/mm^2 plates respectively showed that at 90 deg impact tripling the tensile strength resulted in a quadruple of resistence compard to soft plates while at 60 deg obliquity the difference between 50kg/mm^2 and a 150Kg/mm^2 plate was just 6%-almost identical. This is correct and one of the reasons why relatively soft, aluminium armour plate has replaced steel armour plate in high obliquity applications, since.
My penetration figures are entirely consistent with individual trial data. Note that ESP is more difficult to penetrate in great thicknesses but easier to penetrate in thin ones, caused by the fact that thinner plates from real trials can and have been heat treated more carefully and kept ductile despite higher tensile strength. Thicker plates would be more brittle and thus have to be kept softer. ESP is not changing it´s hardness or ductility properties with scaling up or down thicknesses, unlike real armour plate in real tests.
That beeing said, yes, my data is based upon primary sources for firing trials with known projectile-, plate performance and penetration definitions.
I can exactly determine the penetration of the 75mm Pgr.39 (APCBC with small "Zerleger" HE-filler) at 0 deg(vertical), 30deg, 45deg and 60deg obliquity. I can also exactly determine the plate quality in the individual penetration and I know precisely how these figures communicated in the then classified 1943 source were arrived with. What I cannot determine is the corresponding distance as I have only prooving ground data which do not reference the distance but the striking velocity, instead.
What is needed is a ballistic datafile for the various 75mm gun´s firing this projectile with the drop of velocity plotted against range.
Note that I consider these data much (!) more reliable than data posted in secondary sources, as they are more complete and extracted from a large number of projectile prooving ground (primary..) trials covering low, middle and high obliquities and basically all possible striking velocities in addition to discussions when projectile breakage sets in for specific conditions.
Unfortunately, this conception has turned out as incomplete. While much testing was indeed done in this region, different BHN values were trialed, too (corresponding to 215BHN min and 265BHN max). I have almost all data for the M72 AP from Dr. Allan Hershey´s records at the USNPG and can identify the plate properties from these trials.
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That must be a different report on the same subject, BHN vs. Penetration, that I have:
Watertown Arsenal Laboratory
Report Number 710/607
Problem Number J-1.2
Principles of Armor Protection
Partial Report, no 1
14 April 1944
I wrote a program that calculates relative armor quality based on these tests.
But I am not confident if these small scale tests scale up to real world well.
I have quite a bit. I use it to test my ballistics program.
For the German 75mm/L48:
RANGE..75L48
0m......750
100m....738
500m....691
800m....659
1000m...637
1500m...585
Weight..6.8
3-in,76mm M79
0........2600(792)
500.....2330(710)
1000...2070(632)
1500...1840(561)
2000...1620(494)
2500...1425(434)
Note that such a study similar to yours has been done before. From the tanker's forum:
I only have a document on the M79 giving two points of NBL penetration. The velocity of 4' and 3' penetration. I would like a document on the M79 with more data points. Maybe we can do some document horse trading?
delcyros
Tech Sergeant
If You have that, You will perhaps be interested in some of the files I have, too. The relevant information in the respective context I extracted from DIE VORGÄNGE BEIM BESCHUß VON PANZERPLATTEN, Lilienthalgesellschaft für Luftfahrtforschung 166 (Berlin 1943), in an article written by W. Schilling, EINFLUß DER PLATTENFESTIGKEIT BEIM PANZERDURCHSCHLAG (p.62ff).
Thanks. I will keep a copy but would like to know the source. The relevant perforations for homogenious armour these values and PGr.39 (6.8kg with "Zerleger" , cap and ballistic windscreen) are:
750m/s:
0 deg*: 130mm (85-90 kg/mm^2 tensile strength in trial plates)
30 deg: 103mm (100kg/mm^2 tensile strength in trial plates)
45 deg: 66mm (110-105kg/mm^2 tensile strength in trial plates)
60 deg: ~45mm (extrapolated. Closest penetration was at 850m/s on a 53mm thick, 115Kg/mm^2 trial plate)
691m/s:
0 deg*: 114mm (95-100 kg/mm^2 tensile strength in trial plates)
30 deg: 90mm (100-105kg/mm^2 tensile strength in trial plates)
45 deg: 59mm (110kg/mm^2 tensile strength in trial plates)
637m/s:
0 deg*: 98mm (100 kg/mm^2 tensile strength in trial plates)
30 deg: 80mm (105kg/mm^2 tensile strength in trial plates)
45 deg: 52mm (110kg/mm^2 tensile strength in trial plates)
585m/s:
0 deg*: 87mm (100-105 kg/mm^2 tensile strength in trial plates)
30 deg: 72mm (105-110kg/mm^2 tensile strength in trial plates)
45 deg: 47mm (115kg/mm^2 tensile strength in trial plates)
*using english definition: 0 deg = normal impact. Based upon penetration curves drawn from executed shooting trial, -not theoretical calculation. The plate tensile strength is mentioned. Definition was intact penetration for 0 to 45 deg impact and nose broken for 60 deg, the complete projectile has to pass the plate and deplete it´s energy ("grenz"). Primary source data:
J. Sitz, EINIGE PRAKTISCHE ERFAHRUNGEN IM PANZERPLATTENBESCHUSS BEI DER ENTWICKLUNG VON PANZERGRANATEN ÜBER 3,7cm BEIM HEER, in: DIE VORGÄNGE BEIM BESCHUß VON PANZERPLATTEN, Lilienthalgesellschaft für Luftfahrtforschung 166 (Berlin 1943), 109-113.
If You normalize these data, You may find it helpful to pay attention to the dynamic relationship between obliquity and tensile strength.
I for my part, have never been surprised that no gun defeated the T-54A frontal slope in yugo tests. The front slope was close to 60 deg and no AT- or Tank gun in ww1 had the performance to penetrate a close to 100mm plate in this obliquity range, regardless of ammo type. Unless, perhaps You happen to hit repeatedly the same spot, group impacts close to each other or hit weak spots, which jointly occur.
Hope, it helps.
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I found the 75mm data on 10+ year old posts on the Battlefront Combat Mission site by Rexford (Lorrin Bird, author of WWII Ballistics:Armor and Gunnery). In his post about dispersion and firing tables I found that his 88mm/L71 data matches that of the German 88mm/L71 firing table (which I include it in the PAP.zip) so I am assuming his 75mm is good as well.
I don't know where the links are to the pdfs but I do have them so I uploaded them in zip form to my website. (I'm not going to keep the links up long as I don't want Google or other webcrawlers to link to them.)
Principles of Armor Penetration and the rather large Handbook of Ballistics ... etc which has a few pages on the M79 round.
http://www.panzer-war.com/Files/PAP.zip
http://www.panzer-war.com/Files/HBD.zip
I've tried to normalize my data too but I have to ground them in reality. So...
There's a poster at tank net and WOT named Bojan who posted 1950-1960ish Yugoslav tests where they tested the 76mm M79, 75mm Pak 40 and 76mm Zis-3 on the same targets. Now that is normalized!
I don't know where the links are to the pdfs but I do have them so I uploaded them in zip form to my website. (I'm not going to keep the links up long as I don't want Google or other webcrawlers to link to them.)
Principles of Armor Penetration and the rather large Handbook of Ballistics ... etc which has a few pages on the M79 round.
http://www.panzer-war.com/Files/PAP.zip
http://www.panzer-war.com/Files/HBD.zip
I've tried to normalize my data too but I have to ground them in reality. So...
There's a poster at tank net and WOT named Bojan who posted 1950-1960ish Yugoslav tests where they tested the 76mm M79, 75mm Pak 40 and 76mm Zis-3 on the same targets. Now that is normalized!
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Speaking of the yogo tests.
Let's look at it in a different way. Find the velocity that a shell is travelling at the range that it does penetrate.
Complicating matters we don't know what the muzzle velocity is of the tests.
The 75mm Pak 40 velocity was reduced at some point after entering service. This apparently confounded the US and USSR in testing of the captured weapon such that they at a point listed the muzzle velocity as 770m/s (probably an average of old and new rounds).
In the late war ZiS-3 the BR-350B appears to have an improved version also a BR-350B.
Since I don't know what the muzzle velocity is for some guns I include both for comparison.
Tests on target vehicles:
T-34 46mm@60-deg 350BHN 90mm-rounded 444BHN
..........................glacis..........turret
75mm 750m/s.....1300m=605...1000m=637
or
75mm 790m/s.....1300m=639...1000m=672
76mm M79.........1100m=601.....900m=633
Sherman..... 64mm@47 250BHN... 90-94 rounded 230BHN
...............................glacis.........turret
75mm 750m/s........1100m=626......1000m=637
or
75mm 790m/s........1100m=661......1000m=672
76mm ZiS-3 662m/s..250m=638.......350m=629
or
76mm ZiS-3 680m/s..250m=656.......350m=646
Let's look at it in a different way. Find the velocity that a shell is travelling at the range that it does penetrate.
Complicating matters we don't know what the muzzle velocity is of the tests.
The 75mm Pak 40 velocity was reduced at some point after entering service. This apparently confounded the US and USSR in testing of the captured weapon such that they at a point listed the muzzle velocity as 770m/s (probably an average of old and new rounds).
In the late war ZiS-3 the BR-350B appears to have an improved version also a BR-350B.
Since I don't know what the muzzle velocity is for some guns I include both for comparison.
Tests on target vehicles:
T-34 46mm@60-deg 350BHN 90mm-rounded 444BHN
..........................glacis..........turret
75mm 750m/s.....1300m=605...1000m=637
or
75mm 790m/s.....1300m=639...1000m=672
76mm M79.........1100m=601.....900m=633
Sherman..... 64mm@47 250BHN... 90-94 rounded 230BHN
...............................glacis.........turret
75mm 750m/s........1100m=626......1000m=637
or
75mm 790m/s........1100m=661......1000m=672
76mm ZiS-3 662m/s..250m=638.......350m=629
or
76mm ZiS-3 680m/s..250m=656.......350m=646
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delcyros
Tech Sergeant
What formula do You use to normalize BHN values?
p.s. drop me an email and I can send You some files.
p.s. drop me an email and I can send You some files.
delcyros
Tech Sergeant
Ok, I understand. However, I have some issues here.
[1]
BHN varies -among other things- with thickness of armour (at least in US, british and german sources)
[2] why not use Z-or BCNF-normalisations instead to avoid assymetries?
[3] using 270BHN as a guideline, some of the russian turret armour would be roughly 60% more resistent (at normal impact) than those mentioned above but this isn´t supported by sources.
That's why I didn't include Russians or cast armor. Russian hardened RHA acts well vs. undermatched projectiles. For overmatched not so much: 350 BHN acts like 260 BHN. From yugo tests cast hardened rounded 444 BHN T-34 turret acts like 260 BHN. But then from the same test 230 BHN cast rounded M4A3 turret also acts like 260 BHN.
delcyros
Tech Sergeant
As far as vertical plate is concerned, the drop in quality of russian plates can be explained by impact load failure. This is not exactly the same as impact britellness but it's not ductile anymore. I have some data that indicate that if the plate is not ductile and fails to shatter the projectile's nose, it looses roughly 1/3 of it's ballistic resistence because the plate is much less tough and fails rapidly and completely from surface to back.
Russian armour would fare very well against uncapped and soft capped AP (which it really did) in vertical impact but APC is a different thread, exposing it's lower impact load tensile strength. Small shells may not reach the critical impact load at all.
Russian armour would fare very well against uncapped and soft capped AP (which it really did) in vertical impact but APC is a different thread, exposing it's lower impact load tensile strength. Small shells may not reach the critical impact load at all.
delcyros
Tech Sergeant
Possible, I have very limited data on soviet projectiles and armour plate. But remember, that´s for normal impact. Increasing the obliquity not only enhances protection but also reduces the difference of all qualities. This is correct because at very high obliquity, even water causes regularely a projectile to ricochet off. At high obliquity, a soft but ductile plate has benefits over a hard one even if it´s much softer because
[A] difference in hardness / toughness are less severe than at normal impact
it tends to affect the trajectory of the projectile less during penetration (normalization of impact angle). This effect usually makes intact penetration more difficult for hard plates (body breakage is common) but requires less velocity to penetrate than a similar soft plate
[C] it can cause EASIER penetration for soft capped and uncapped AP due to nose shatter or body breakage which cause the changed projectile nose (blunter now than originally) to bite better in the plate
[A] difference in hardness / toughness are less severe than at normal impact
it tends to affect the trajectory of the projectile less during penetration (normalization of impact angle). This effect usually makes intact penetration more difficult for hard plates (body breakage is common) but requires less velocity to penetrate than a similar soft plate
[C] it can cause EASIER penetration for soft capped and uncapped AP due to nose shatter or body breakage which cause the changed projectile nose (blunter now than originally) to bite better in the plate
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