Alternative light and anti-tank guns, 1935-45

A few "rules" of thumb for close range penetrations.
Conventional AP at 2000fps (610ms) can perforate about 1.3 times the projectile diameter.
Conventional AP at 2600fps (792ms)can perforate about 1.8 times the projectile diameter.
Conventional AP at 3500fps (1067ms) can perforate about 2.8 times the projectile diameter.

Now there are a few problems here, this is theoretical and steel does not work in real life like in theory.
Conventional AP shot (uncapped) tends to start failing somewhere near 2600fps,
Conventional capped AP shot tends to start failing at somewhere 3000fps.
Which brings in the need for either tungsten carbide or special steels with very high tungsten content. There were ways to get around using Tungsten but they usually required other rare elements. Without knowing the types of steel just saying "steel alloy penetrator doesn't tell us much, as mentioned earlier, some types of steel can contain 17-19% tungsten while other steels that do the same job might only have 1.5% but use much higher amounts of molybdenum, vanadium, or cobalt than the high tungsten steels. Tungsten carbide is not just a mix of Tungsten and carbon but used about 25% cobalt as a cementing agent.

Note that is is impact velocity which is usually lower than muzzle velocity.
Also note that projectile that hits a plate at very high velocity and well exceeds the penetration needed to 'just' penetrate doesn't really matter if the tip shatters.
Long barreled 88mm doesn't care if the tip shatters on the front hull of a Sherman, the broken projectile is going right on through the front plate, the firewall, parts of the engine and right on through the rear plate.
Of course the Germans paid for this extra penetration with a very large gun, large powder charge and high barrel wear.
Soviets got high penetration at 2600fps by using 122mm guns. Barrel wear may have been lower but really big gun and large powder charge.

for longer ranges larger bore guns hold their velocity better. Of course a tank only has so much space to fit ammo into so large guns have fewer shots in the same size tank.
Anti-tank guns need more trucks to carry larger ammo.

Hollow charge rounds changed quite a bit in just a few years. So did APCR and APDS rounds and with it taking several years to design a gun and get into production one type of projectile maybe favored and then fall out of favor during a guns design/testing/ production phases.
Depending only one type of AP projectile makes defending against that type of projectile easier.

Large guns also have high recoil forces. However lighter weight APCR/APDS shot reduces recoil compared to full size shot.

So do lighter than normal HEAT rounds. But lightweight heat rounds have rather poor down range ballistics.
Very early rifled HEAT rounds had trouble penetrating armor equal to their own diameter. This got a bit better during WW II. A lot better after WW II. There were also problems fusing and a number of HEAT rounds were fired at lower than normal velocities, even for howitzers, so the fuse could function and initiate detonation at a decent stand off distance. The low velocity curved trajectory made hitting hard at all but the closest ranges.

There were a lot of conflicting requirements.

Shortround6 said:

Which brings in the need for either tungsten carbide or special steels with very high tungsten content. There were ways to get around using Tungsten but they usually required other rare elements. Without knowing the types of steel just saying "steel alloy penetrator doesn't tell us much, as mentioned earlier, some types of steel can contain 17-19% tungsten while other steels that do the same job might only have 1.5% but use much higher amounts of molybdenum, vanadium, or cobalt than the high tungsten steels. Tungsten carbide is not just a mix of Tungsten and carbon but used about 25% cobalt as a cementing agent.

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Germans were trying hard to find replacement for tungsten for armor piercing. At the end of the day, their conclusion was that tungsten is still the king.
They were also low on availability of the cobalt. Cobalt mixed with other materials (seems like also the tungsten was needed here, as well as chromium) was part of the recipe for the stellite - the material that was widely used as the coating of the engines' exhaust valves. Once French N. Africa was in the Allied hands, supply of cobalt for the European Axis was badly hurt.

How much superior tungsten was vs. the best steels, even while keeping the MV under 1000 m/s? The MK 103, firing the 350 g APCR shot at 960 m/s, was besting the next best competitor - the 25mm AT shot of 320 g fired at 950 g - by almost a double penetration value; that shot of the 25mm gun was with the hardened steel core of 210g.
(that was the hottest loaded cartridge of the 25mm ATG - that gun was also firing the 'normal' loaded cartridge, that went out at 920 m/s)

Hmm - one wonders how good would've been the captured 25mm gun with the 'proper' APCR shot that has tungsten core?

I would note that while the British got APDS shot into service in 1944 nobody else did. I don't know about the accuracy of the 6pdr but there are number of stories about 17pdr.
British did use APDS in the 20pdr in 1948.
The Americans didn't use APDS in the 90mm M-26 through M-48 series and only adapted APDS with the British/NATO 105mm.
On the other hand the British rarely used HEAT ammo in much of anything. Much preferring HESH (HEP in the US).
Companies that made ammo for US tanks supplied to NATO or other areas of the world could build/sell whatever they wanted but they had many years after WW II to sort out any problems.

doesn't matter what APDS will go through if you can't hit a tank with it unless at very short ranges.

tomo pauk said:

How much superior tungsten was vs. the best steels?

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Book published in 1968 says sintered tungsten carbide with about 25% cobalt has a density of 13g/cubic cm.
"Steel" is listed as 7.85 g/cubic cm but

Shows a low (?) of 7.75 g/cubic cm and most steels and stainless steel topping out at about 8.00.

Tool steel shows an even greater variation but even T 1 tool steel (the tool steel with 17.5-19% Tungsten) is 8.67 g/cubic cm.
Tool steel may have properties that aid in penetration but the change in density is not a big one.

Making a "core" out of tool steel still leaves you with a very light projectile/penetrator and while you can reach a high muzzle velocity, impact velocity may be lower than the tungsten core and the higher density core may penetrate better even at a lower velocity. A lot depends on the sizes of the cores and velocities.

tomo pauk said:

Germans were trying hard to find replacement for tungsten for armor piercing. At the end of the day, their conclusion was that tungsten is still the king.
They were also low on availability of the cobalt. Cobalt mixed with other materials (seems like also the tungsten was needed here, as well as chromium) was part of the recipe for the stellite - the material that was widely used as the coating of the engines' exhaust valves. Once French N. Africa was in the Allied hands, supply of cobalt for the European Axis was badly hurt.

How much superior tungsten was vs. the best steels, even while keeping the MV under 1000 m/s? The MK 103, firing the 350 g APCR shot at 960 m/s, was besting the next best competitor - the 25mm AT shot of 320 g fired at 950 g - by almost a double penetration value; that shot of the 25mm gun was with the hardened steel core of 210g.
(that was the hottest loaded cartridge of the 25mm ATG - that gun was also firing the 'normal' loaded cartridge, that went out at 920 m/s)

Hmm - one wonders how good would've been the captured 25mm gun with the 'proper' APCR shot that has tungsten core?

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Quoting WW II German APDS projects? : "In Hogg's German Artillery of WWII, he talks about work on a 7.5cm Pzgr PAK Patr TS42, a 6cm APDS using a steel core. Projectile weight 2.74kg. If the late war document I referenced in my earlier post is correct, then this work was dropped as part of a general disenchantment with APDS." (I don't have that book so cannot say anything more about this). So indeed, it seems they were trying various options to get good penetration without tungsten.

For another, albeit more contemporary comparison between steel and tungsten, see cold war Soviet 125 APFSDS projectiles at 125MM APFSDS ROUNDS . Comparing 3BM9 with 3BM12, where the 3BM9 is maraging steel and the 3BM12 is maraging steel with a tungsten penetrator you have 240 vs 280mm penetration (2000m at 0 deg). Later penetrators get massively better, but hard to do a 1:1 comparison as there are other changes as well.

Also a thread from a decade and a half ago, with some of the same participants as this thread so far: Panzergranate 44 - German APFSDS

The Germans were experimenting with fin-stabilized sabot projectiles, but it seems for long range artillery, flak, and even concrete bunker busting: Peenemunde Arrow Shell . But strangely(?), no effort to use this approach for penetrating armor steel in tanks. But as seen historically, while the concept itself is straightforward enough on paper (long penetrator giving good sectional density, which means must discard spin stabilization => smoothbore gun, which means needing fin stabilization => APFSDS), it seems it took quite a lot of work to actually make it work in reality.

But speaking of smoothbore guns, maybe their best bet would be a light-weight medium velocity smoothbore gun firing HEAT? Like the PAW 600 and planned PAW 1000. The downside of course is harder to hit moving targets.

z42 said:

But speaking of smoothbore guns, maybe their best bet would be a light-weight medium velocity smoothbore gun firing HEAT? Like the PAW 600 and planned PAW 1000. The downside of course is harder to hit moving targets.

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IMO, the breech-loading mortar as-is would've been just fine, working against the armored targets with HEAT and against softer targets with HE. Or, we can consider them as the cheap infantry guns that are also doing decently against the tanks.
The HEAT shell will take advantage of it's light weight so it can sport the greater MV than it will be the case with the usual HE shell.

A step further might've been the rifled bore weapon, that still uses the mortar ammo. More expensive, but more accurate.

Another idea might've been the mortar-based weapon that has the hole halfway down the bore, with another tube made from sheet metal attached to it and facing backwards. Not really a recoilles gun, but might be toning down the recoil a bit without kicking up the dust as the true recoilles gun will do.

Elan Vital said:

The Soviets on the other hand consistently had to deal with inferior propellant which resulted in somewhat bigger charges than Western equivalents (or limitations owing to the pressure curve of said propellant).

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Very interesting. Do you have some data to elaborate the point?

tomo pauk said:

IMO, the breech-loading mortar as-is would've been just fine, working against the armored targets with HEAT and against softer targets with HE. Or, we can consider them as the cheap infantry guns that are also doing decently against the tanks.
The HEAT shell will take advantage of it's light weight so it can sport the greater MV than it will be the case with the usual HE shell.

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There was a fusing problem with many of the early HEAT shells.
The Pak 97/38 use AP shot at 570m/s
The HEAT round at 4.54kg was fired at 450m/s.
The Pak 40 fired a very similar projectile at 450m/s also.
The 8cm PAW fired a 2.70kg HEAT projectile at 520m/s.
The 8cm PAW fired a 4.46kg HE shell at 420m/s using the max charge of a 3 charge system.

If the HEAT shell hits at too high a velocity the nose crumples as it hits and the shaped charge gets closer to the target and the jet doesn't have the right stand off distance to form up and work. You get less penetration with higher velocity even though you get better "accuracy".

tomo pauk said:

A step further might've been the rifled bore weapon, that still uses the mortar ammo. More expensive, but more accurate.

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If you use rifling you degrade the performance of the shaped charge. The spin imparts a centrifugal force to the shaped charge jet which spreads it out. Shallower hole but wider.
The 8cm PAW was already rated at 160mm of penetration which was considerable better than the 10.5cm howitzer (100mm?).

We are also dealing with two different meanings of "Accuracy". One meaning is how many shells you can get into a specified size target at a known range. Low veleocity guns can actually do rather well at this.
The other meaning is how easy it is to hit a given target at a unknown range. High velocity guns are much better at this.
Big question is if there is a cross over and/or where is it. British 17pdr guns with APDS had super velocity but for some reason (a number of arguments/theories) they couldn't keep even 1/2 their shots on a Panther tank at some of the test ranges. Bad batch of ammo or????
A short/light rifled 75-90mm gun using HEAT ammo may have put a higher percentage of shots into the same target as the 8cm PAW but it might not have done any better at guessing the range and the spun shells would not have penetrated as much armor.

tomo pauk said:

Another idea might've been the mortar-based weapon that has the hole halfway down the bore, with another tube made from sheet metal attached to it and facing backwards. Not really a recoilles gun, but might be toning down the recoil a bit without kicking up the dust as the true recoilles gun will do.

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Part of the problem is timing and part is how much recoil reduction do you want.
I have seen a gun something like you describe but I don't know where to look now.
The timing problem is that the gun starts moving backwards under recoil and not when the projectile leaves the barrel. Muzzle brakes do sort of the same. They lessen the total recoil impulse.
If you tap gas of the barrel you lower the velocity and to get any substantial reduction in recoil you have to direct a lot of gas somewhere else. German and American Recoilless guns used about 4 times the propellent at a normal gun firing the same projectile at about the same velocity. One reason the German supply guys didn't like recoilless guns.
If you only redirect an equal amount of propellent gas you don't get a major deduction in recoil.
There are ways to kick up less dust with the muzzle brake. Like cut the ports at an angle to direct the blast upwards and not sideways. Like a small arms compensator.
If you use a tube to direct blast up and backwards you still have the problem of keeping the rear arc clear and using the weapon in a confined space is still a problem.
Even if a lot less than a German/US RR.

tomo pauk said:

Very interesting. Do you have some data to elaborate the point?

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The history of the use of Lend-Lease powders is described in some detail in this book:

Well, and of course, there everything looks not quite as it sounded in the thesis, or not at all - depending on the bias.
Western powders were used mainly for larger calibers (from 100mm), provided that their share in the charge does not exceed 25%. For smaller calibers the results were unacceptable due to the geometry of the powder and its high caloric content. Barrel pressure increased by 2% with mixed charges.
And in general, the thesis is somewhat surprising - the charge in the ZIS-3 shell is 1 kg, whereas the Pak 40 has a 2.7 kg charge.

In addition, just in case. The author is a participant of the described events, but, as I find, adheres to a rather critical point of view on the events and adequately describes the role of lend-lease supplies. This is not Soviet propaganda, but rather eyewitness reports.

Oh, I forgot about American pyroxylin powders. There were also many problems with them, but they were partly solved by adding dinitrotoluene and dibutyl phthalate, and for 85mm the Soviets changed the charge design. American powder for the 3" anti-aircraft gun was used for Soviet 76mm charges only for the Model 1902/30 gun, both in pure form and in a mixture due to changes in technology.

A couple more interesting facts: in 1943, all glycerin in the USSR, as well as 78% of ethanol and 62% of centralite were obtained by lend-lease.

Shortround6 said:

We are also dealing with two different meanings of "Accuracy". One meaning is how many shells you can get into a specified size target at a known range. Low veleocity guns can actually do rather well at this.
The other meaning is how easy it is to hit a given target at a unknown range. High velocity guns are much better at this.

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There are no two definitions of accuracy. It is defined in the firing tables by the parameters of the scattering ellipse for a given distance.

bf109xxl said:

There are no two definitions of accuracy. It is defined in the firing tables by the parameters of the scattering ellipse for a given distance.

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I am a target shooter. Accuracy to me, in a match with known distance, is the group size the gun/ammo makes. Vertical target. For artillery with a horizontal target that turns into an ellipse. Same width pattern (proportional to range) but the vertical on the vertical target gets spread out in distance on the horizontal target forming the ellipse.

However in the field (combat or hunting) in the days before hand held laser range finders, There was a lot guessing as to range and a lot of wrong guesses. High velocity guns had a shorter time of flight for moving targets and they dropped less and and could make up somewhat for a poor guess (or at least hit closer) as far as range went. The guns/ammo may not have been more "accurate" but they got better results or did it faster/with less shots for correction.
To the men using the guns it might have seemed they were more accurate (they missed less).
Germans may have more rangefinders around.

Allowing for better guessing for the 1st round shots.

Now the mounts and sights also play into things here. A gun that is "accurate" at 700meters will not usually gave poor accuracy at 1100-1200 meters. The "spread" should be in proportion. 50% greater distance should mean a 50% (or slightly greater) larger spread/pattern.
But the British screwed over their troops in the tanks and unlike the Germans (and everybody else) who could adjust their elevation with a screw adjustment for the 2nd or 3 rd shot the British gunners had to balance the gun on the shoulder piece and hold the cross hairs over the target and since the gun moved a lot more under recoil practical accuracy was dismal compared to the German tanks. British rated the 7.9mm ammo and gun in the turrets of their tanks at 800yds or meters. German tank sights went to 1200 meters (or more) the 7.9mm ammo. British ammo really that bad or the sight system and mount did not allow the guns/ammo be used up to it's potential?
Small guns in the dessert needed better range estimates once they got much past 700-800 meters.

Light guns that bounced around a lot between shots also had problems. The gun/ammo may have been accurate on the proof range but having to relay the gun because the gun moved both takes time and reduces "accuracy." Or perhaps consistency is the word we are looking for. But if an officer/soldier in his memoir uses the word "accuracy" how should we interpret it?
To him the bullets/shells were not going where he wanted them to go.

Shortround6 said:

I am a target shooter. Accuracy to me, in a match with known distance, is the group size the gun/ammo makes. Vertical target. For artillery with a horizontal target that turns into an ellipse. Same width pattern (proportional to range) but the vertical on the vertical target gets spread out in distance on the horizontal target forming the ellipse.

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If it sounded like "to me accuracy means..." then I wouldn't be arguing. But there is only one definition of accuracy used in artillery. Soviet firing tables give three parameters: range deviation, vertical deviation, and side deviation. Hit probability is a different term.

Accuracy: the measure of mean point of impact (MPI) deviation from the desired MPI.

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Indirect Fire: A technical analysis of the employment, accuracy, and effects of indirect-fire artillery weapons
by O. S. Dullum, K. Fulmer, N.R. Jenzen-Jones, C. Lincoln-Jones and D. Palacio
ARES, January 2017

bf109xxl said:

Indirect Fire: A technical analysis of the employment, accuracy, and effects of indirect-fire artillery weapons

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Thread is about light guns and anti-tank guns.
Anti-tank guns primary role is direct fire.
Infantry guns is often direct fire, although there is a lot of indirect fire too.

British 6pdr and 17pdr guns using APDS were firing direct. Also full bore projectiles were used for direct fire.

We can argue about definitions for weeks or months. Most of the men who wrote about their experiences in the WW II have passed on and we are left trying to figure out what their writings mean. Often they did NOT include shot patterns or other test numbers.

Hit probability is a different term. Unfortunately it may not have been used when it should have been.
And accuracy, in a direct fire situation is just one aspect of hit probability.

Shortround6 said:

Thread is about light guns and anti-tank guns.
Anti-tank guns primary role is direct fire.
Infantry guns is often direct fire, although there is a lot of indirect fire too.

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It doesn't make any difference. The definition remains the same. The tables are the same for any type of fire.

Shortround6 said:

British 6pdr and 17pdr guns using APDS were firing direct. Also full bore projectiles were used for direct fire.

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Like the ZIS-2. But in the firing tables only the values of the scattering ellipsoid axes are given to describe the accuracy.

Shortround6 said:

We can argue about definitions for weeks or months. Most of the men who wrote about their experiences in the WW II have passed on and we are left trying to figure out what their writings mean. Often they did NOT include shot patterns or other test numbers.

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I'm not interested in anyone's experience. I'm interested in definitions. We can end the dispute very quickly - just cite an official document related to artillery where accuracy is not treated as a measure of dispersion at firing.

tomo pauk said:

French N. Africa was in the Allied hands, supply of cobalt for the European Axis was badly hurt.

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Shortround6 said:

British gunners had to balance the gun on the shoulder piece and hold the cross hairs over the target and since the gun moved a lot more under recoil practical accuracy was dismal compared to the German tanks.

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This was a deliberate choice that allowed firing on the move. A crude gun stabilisation that was founded upon the 1885 way light QF guns were mounted on ships which always move. The first tanks had such (Ordnance QF Hotchkiss 6 pounder gun Mk I and Mk II or QF 6 pounder 8 cwt, later 6cwt) ex naval guns and they found firing on the move useful and a good experienced gunner was found able to fire on the move on typical ground quite well and it was well trialled and practiced in comparison with stopping to fire. The limit of human power was reached with the 6 Pounder and the similar QF 75mm. It sadly came with installation issues in order to have the gun balance able by a normal human. A gun for firing did not need such a balance as the weight was taken by the elevation device not the gunner. A consequence was that the shoulder controlled gun required an internal mantlet whilst the mounting controlled gun could have its mantlet external.

As guns grew heavier the shoulder controlled fire on the move lost its utility and later stabilisation systems did the task mechanically. Essentially the British system was not unsound nor untested. It was a system that only existed usefully in a brief window of technical development. Simple and effective in the right hands but rendered obsolete by gains in the mass of tank guns and automatic stabilisation systems. The right answer at the right time but the wrong answer in later times.

Elan Vital said:

The 88mm KwK 36 had relatively similar power to the Soviet 85mm tank guns, but the latter put a lot of effort in the development of a compact mount so the installation was a good deal narrower. The KwK 43 in the Tiger II was reworked with a much more compact mount as well which is a good part of why the narrow turret front was possible in spite of the increased power of the gun. The Panther improved on the Tiger I to some degree, but introduced other problems (very front heavy turret), and it's only with the Schmalturm and reworked mount that the 75mm L70 became truly compact.

There was a similar situation with the 75mm M3 and 76mm M1 in the Sherman as opposed to the British 75 and the Soviet 76mm guns

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Classifying cannons in a slightly different way, showing muzzle energy

Shortround6 said:

The Americans didn't use APDS in the 90mm M-26 through M-48 series and only adapted APDS with the British/NATO 105mm.

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Used similar HVAP, tungsten carbide core within a lightweight full caliber body, no discarding after firing.

Sifting through some web resources, the 'Jaegerplatoon' website gives some interesting data for the Soviet 76mm AA gun firing the Finnish-made APC shot at 20 deg sloped armor (or 70 deg, depending on what side of the pond one is ). Supposedly at 1000m it was able to pierce 125mm (almost 50% more than the Pak 40 against the 30 deg sloped plate) - IOW the Tiger I tank is a fair game at that distance. Or, barely worse than the Tiger's gun at the same distance??
J Juha3 - help

The charge of the Soviet 76-mm antiaircraft gun shell was 1.4 kg, the muzzle velocity was 813 m/s. Either the cores for Finnish shells were forged by Ilmarinen himself, or something is wrong with the figures. In addition, the range dependence of armor penetration looks unusual.
Sounds like a runic song from the Kalevala to me, but sometimes miracles happen - I can't deny the facts (but a primary source would be nice to see).

bf109xxl said:

Either the cores for Finnish shells were forged by Ilmarinen himself, or something is wrong with the figures. In addition, the range dependence of armor penetration looks unusual.

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Yes, the penetration figures do look very suspicious.

BTW - since there was a talk about the APCR-lookalike shot that has a steel penetrator instead of tungsten, there was several guns that might've used it. Like a host of the 75-76mm guns that were good for about 700+- m/s. Includes the Soviet F-22 76mm guns, the French 75mm AA long-barreled guns, as well as the 7,5cm lefk N.A. The later were capable for firing a 1250 g propellant charge, vs. for example the old French 75 gun that was rated for a propellant of 750g (kicking and screaming while doing it ) for well under 600 m/s, at least in the AA role.
Perhaps some 850 m/s would've been achievable with the 'cheapo APCR'?

Heck, the new French AA guns would've been decent AT guns on their own, with an APC shot. With less than 200 captured, and without offering anything to the LW apart from being free, prying them away to be used by Heer should've not been much of a problem.