Alternative light and anti-tank guns, 1935-45

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Shortround6 said:
They screw up your camouflage and make you easier to spot and they make it hard to see where your shells are landing.
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Seems US Powders often not as flashless or smokeless as the German, so already at a deficit
tomo pauk said:
Matilda have had a turret with a 6pdr mounted for trials (the trials maybe never happened?);
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Or bigger





Which means theoretically could have had the KV II turret
 
tomo pauk said:
Thanlk you again.
BTW - is there an accessible place to take a look at the different, new (for the time) French ammo types? Anything between 7.5mm to 155 mm is a fair game
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Not to my knowledge. The website Wikimaginot is the closest thing to it since it gathers pictures of the ammunition of most guns used in fortifications (and links to relevant pages):
 
The French were using Tungsten alloy tool steel for penetrators, not tungsten carbide.
You do not get some of the benefits of Tungsten carbide (like the much greater density/weight per unit of frontal area for the penetrator)

Guessing here but perhaps the use of tungsten alloy tool steel allowed for easier fabrication? One piece penetrator with uniform heat treatment?
A lot of AP shot varied the heat treatment from nose to tail with the tip being very hard and the shoulder/body being softer. Getting consistent heat treatment called for skilled workers.
The French 25mm ammo is very much like a rifle or HMG bullet. A steel core (French used fancier steel) a lead filler in the tip and a brass (not copper or gilding metal) jacket holding everything together.

The French 37mm APCR round is interesting but it's wide spread adoption may be questionable. It does offer an avenue for lower velocity guns to get improved penetration.
Advantages for higher velocity guns are somewhat more doubtful. Or they are trading short range advantage for long range disadvantage.
APC shot works with a softish nose cap to both pre-stress the armor and to spread the impact load out to the shoulders of the projectile while the 'supported' tip punches through instead of shattering into pieces. How well tool steel works instead of this combination different steels and heat treatment is certainly subject to question and perhaps trials were conducted by somebody somewhere using tool steel and the answers are hidden in some file somewhere.
At any rate, to try to use the tool steel penetrator in a larger gun, like a 75mm field gun, we may run into a problem. We can certainly increase the MV. The T45 HVAP round in the Sherman went to 2850fps vs the 2030fps of standard AP shot, about a 40% increase. But the shot weighed 8.4lbs instead of the normal 14-15lbs. With tungsten carbide you get a very heavy, dense penetrator. If you use tool steel you get a penetrator not much different than regular steel, which leaves several choices. A similar sized penetrator core is going to be under 1/2 the weight. You can drive even faster, but you have under 1/2 the energy at impact trying to move the target steel out of the way. And a lighter APCR round is going to loose velocity quicker. You can make the penetrator a little fatter and a little longer to get the weight (punch) back up but that also means you are trying to make a larger diameter hole.
US T45 shot had 473 ft tons at the muzzle, the M61 shot had 427 ft tons and the M72 shot had........398 ft tons. The T45 was concentrating more of it's force on that smaller penetrator.
If you make the all steel penetrator bigger you are spreading the force out more. But the less dense material also means you have less force in the penetrator to begin with and more force (percentage wise) in the collar/jacket that is being scattered/smeared over the face of the armor.
A steel penetrator of identical shape (diameter and length) to the tungsten carbide penetrator is going to have about 1/2 the penetration.

US M93 HVAP from the 76m gun.
 
Getting back to the title of the thread.
Alternative light and anti-tank guns, 1935-45
We have the problem of a 10 year time span with several 'technologies' showing up just about in the middle.
First use/issue of shaped charge was in fall of 1940 in the west (?) and a few showed up with the German forces in France. Neither was really that good.
Tungsten Carbide as opposed to Tungsten steel pretty much showed up after the Battle for France except for The German and Polish AT rifles and the German 37mm AT gun?
By 1941 the Germans were stuffing Tungsten Carbide is just about everything and had derailed the main AT gun train with the taper bore nonsense.

Trying to combine a light AT gun with a light infantry support gun is very difficult specification to fill.
Germans show this with the IG 18 which weighed about 400-440kg and could fire a 7.5cm shell holding 570g of HE and smoke charge to make observation easier. A later round changed the HE content to 670g of 1 90/10% mix of TNT and aluminum (bigger flash?), There was also a smoke round with blue smoke for target marking and they did issue one or more HEAT rounds (when?).
Now the Germans had the 3.7cm Pak that weighed around 430kg (different wheels?) and it's HE shell held about 25g of HE, some sources claim there was a later HE round that didn not have a tracer that held 40g. Better than firing AP shot for infantry support but one can see why they wanted two guns. Germans also started issuing the two small taper bore guns.
The 28/20mm PZB 41 which was commendably light at about 230kg and could poke a hole in rather thick piece of steel, 52mm at 30 degrees at 500 meters and a lit more close in. Trouble was it was a small hole.

Penetrator was 10.9mm in diameter.
There was the HE round as shown but it only held 5g of HE. Germans made about a 1/2 million of the HE rounds for what may have been near total waste of time/effort.
The Gun was expensive to make, and the barrel wore out quickly. Wearing out the barrel shooting such small HE loads doesn't sound like a good idea. In any case they made just under 2800 of the guns.
Germans followed this up with the 4.2cm Pak 41 which was a taper bored barrel on a 37mm AT gun carriage. Weight was 560-642kg (sources differ) for a rather impressive penetration. 53mm to 60mm at 1000 meters depending on angle, sources only agree occasionally on what happened closer. Problems were much the same. There was an HE round but since it is listed as weighing about 280g and it was far from being a 'mine' shell it is unlikely to be as effective as the normal 37mm AT gun. Around 310-315 built?
The German 50mm AT gun is 990kgWe have been over it before.

The Czech 47mm may have potential, it offers 52mm at 1000 meters at 0 degrees? and 69mm at 500 meters? it is listed at 590kg although that is with horse traction wheels and weight may go up with better wheels/tires. It does offer an HE shell with around 165 g of HE (depends on exact type/method of filling. As usually with under 75 (70?) mm guns smoke is not on the menu.

What weight are people willing to deal with?
What armor penetration are they looking for?
At what distance and that includes both penetration and distance. German IG 18 fired it's early HEAT round at 260ms making it a very short range preposition.
What kind/s of other capabilities are being looked for? How much HE and/or smoke/cannister etc.
The extreme AT guns like the German taper bores have an awful lot of negatives even if a country has Tungsten Carbide.
 

I'd like to note that the requirement in this thread is not to have a single design for both the tasks. If one can do it - great; if not - not a problem.

Eg. Germans (and other people, like Polish, Italians, French, British, Japanese, Americans etc) can make a breech-loading 81mm mortar for the role of the 75mm infantry guns. The barrel can be lightly rifled for greater accuracy. Advantage: infantry unit has one ammo type less to worry, and can use any captured 81mm mortar ammo, that was probably the most wide-spread type of ammo in the 1930s. Another advantage: once HEAT ammo is introduced, the gun can be a good hole puncher, instantly and on a dime. The mortar ammo was made of the lower quality steel = it is cheap, and can be produced in factories that are not that well outfitted like what the big companies like Vickers, Puteaux, Krupp or Rheinmetall.
 

Thanks for listing out all these numbers.
If the use of tungsten carbide for the small guns is in the cards (and it seems like it was), Germans could've simply made the single shot or semi-auto gun that fires the 30mm ammo from the MK 101. All the hoopla wrt. the fancy barrels and the extra ammo type is removed from the equation, and the HE shell is actually useful at 440g.
Penetration is/was in the ballpark with the 28mm Pzb.

Saying that Czech 47mm gun had the potential is selling it short. As we can see, it can deal with most of the French tanks of 1940, unlike the Heer's & LW 37mm guns. Germans missed the opportunity to have the Pz-III armed with the 47mm gun already during the winter of 1939/40.
Make the APCR ammo a bit longer barrel for it for extra oomph, that, together with the 5 cm pak, makes it possible to skip the 42mm all together.

Use of smoke shells can be left to the infantry mortars.
 

Problem with the German light gun was that the barrel length was too short, at about 12 calibers. The next iterations fired the similar ammo (nominally the same ammo, but it seems that it used bigger charges) through the longer barrel, and gained 40-50% greater MV, for the cost of increased weight (510g vs. 400).
Germans, same as vast majority of other people, were slow to adapt the cored layout of the shell. Even the French, 1st people that did the thing, were making them only for the short 37mm gun. That ammo was also exported in Poland. Main benefit was that MV was up by some 50%, and the penetration more than doubled. Couple the cored shot with the longer barrel on the infantry gun and it can do much better wrt. armor penetration.
 
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AMX 10 TCM 81. direct fire mortar gun

poll caid’s suggestion #101 I would like to suggest an interesting tank for the French, the AMX 10P TCM 81 the AMX 10 TCM 81 was an 81mm tank presented for the first time in Satory 1981. the tank...
forum.warthunder.com
won't let me link to their photos.
Nobody bought it.
Yes there was an APFSDS round for this thing. It was a steel dart with fixed fins. I grabbed the above photos from the net but I do have photo/s in an old book but I have to scan it.
You either have a smooth bore or you don't. Mortar bombs of the time did not have a copper/brass sealing ring. They bounced down the bore and bounced back up it
There was no way to engage the rifling and you were going to beat the crap out of the rifling firing iron or steel projectiles out the barrel.
The US got around that with their 4.2in mortar by screwing a curved metal disk to the rear of the bomb bomb and using the gas pressure in the barrel to push the edge of the disk into the rifling. US changed mortars in 1951-52 a perhaps again, at some point they got engraved rifling bands around the body of the shell.
Once you lower the barrel a certain amount for horizontal fireyou have the entire contraption siding along the ground, Mortars depend on the base plate recoiling into the ground.
Yes you can use a heavy mount, and/or use a recoil system but then the whole cheap and cheerful aspect goes away.
Few people got away with it with 50/51mm/2in mortars.

80-82mm mortars (Soviets used 82mm with the idea they could use German (or other) bombs but the Germans couldn't use theirs)
WW II mortars were generally pretty poor accuracy wise. Things got a lot better in the 1960s so comparisons take a lot of figuring out as to who was using what when. British moved the whole mortar accuracy thing a least 1 order of magnitude with their 81mm mortar in 1961.
 
A brass ring 'installed' just behind the widest part (ribs/rings)of the mine might've worked well?


The small casing was used on ammo for breech loading mortars for decades. See the 100(105)mm mortar shells here, for example.
Ammo is still cheap - even free - even if the gun is not very cheap.
 
French short 37 with cored shot didn't even reach what the French long 37mm (and with a 33 caliber barrel it wasn't that long) did.
Basically people were slow to adopt the cored shot because it didn't do much for the higher velocity guns. High being a relative term.
General rule of thumb is that an AP shot doing 2000fps (610ms) can penetrate 1.3 times it's diameter at the muzzle, The US 75mm was going through about it's diameter at 500yds (457meters) sloped at 30 degrees. The French shot with a MV of 600ms was going though about 57% of it's diameter at 400 meters at 35 degrees. Granted this was over 2 1/2 times what the old AP shot did 388ms.

But lets take a look at the German 37mm AT gun with it's normal velocity of 2500fpm and it's AP40 velocity of 3379fps and it's projectile weights of 680g and 368g.
Just sticking a steel core in place of the tungsten carbide core will make the shell lighter and give it a bit more velocity, unfortunately the core will have about 1/2 the energy of the carbide core. And at close range you are exceeding the limits of even tool steel to prevent breaking up.
You can make the core bigger to retain weight, back to near the 3379fps/1020ms velocity (still very high ) but now you are trying to make a bigger hole. If the original core was 15.7mm in diameter and you use a 17.27 steel core you are now trying to make a hole 21% bigger.

Longer barrels help, somewhat. Most of the time longer barrels got larger powder chargers (bigger chambers). The US 75mm got a barrel 9 calibers longer (31 to 40 calibers in length, 29%) and increased it's MV by 180fps ( 9.7%).
 
tomo pauk said:
A brass ring 'installed' just behind the widest part (ribs/rings)of the mine might've worked well?
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Even most 120mm mortars depend on gravity to load, Bomb is dropped into the bore and as the bomb drops down the air has to get around the bomb or else it slows the bomb down and you get light strikes on the primer and the occasional misfire. Different propellants left different amounts of soot/fouling in the barrel so clean and dirty (used) barrel don't quite operate the same. On the photo you provided there are 4 groves machined into the bomb body. The forward edge is about 90 degrees and the rear edge has a considerable slope. The air can get by the bomb if it was dropped down a mortar barrel (without the cartridge case) but when fired the gases rushing up the space between the bomb and the barrel hit the groves and try to turn 90 degrees, This does two things, it does slow down the escaping gases ( more range) and it tends to float the bomb on a cushion of gas in the barrel helping center the bomb in the bore. That is the idea, how successful this was?
British took 4 years to put something like a piston ring around the bomb

The rearward Part of the ring is shaped so that the expanding gases push the ring into contact with the bore and seal a greater amount of the gases inside the tube. The forward part of the ring is shaped so that the ring centers the bomb up in the bore and with much more accurately machined fins (no longer stamped sheet metal) the bomb is now much more accurately located in the bore. Work started in 1957 for the 1961 issue date. There were other changes, like a bomb material that offered much better fragmentation. It was a much, much better bomb, but cheap and cheerful cast iron bombs and stamped/riveted fins were history.

You could have a tighter fitting bomb and use a lanyard operated firing pin on the muzzle loaders. But that has few problems of it's own.
tomo pauk said:
The small casing was used on ammo for breech loading mortars for decades. See the 100(105)mm mortar shells here, for example.
Ammo is still cheap - even free - even if the gun is not very cheap.
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you just have to willing to accept the trade-offs. Once you try for better accuracy than most WW II mortar bomb bodies and tail fins and smooth barrel give you things start to get expensive quick.

French were making mortars with this system in the early 50s (maybe earlier?) but you need to rifle the barrel, fit the and engrave the rifled band, Use care loading the bomb and so on. Gives much better range and accuracy than WW II mortars. Cost a lot more too, even if cheaper that full Howitzers.
 
Other people put the rubber ring on the modern mortar shells.
The 'much better' bomb was already in production well before ww2:



Same 'long' bomb was used by Poland, Italy and, presumably, France. It carried 4 times the HE filling vs. the short bomb (2 kg vs. under 500 g).
It took Germans until 1940 to introduce their equivalent?
 
The US also used a long bomb but it lost favor during the war. In part because of the decreased range.
The long bomb body was often used for the smoke and illuminating rounds.
The US had tried using fold out fins before WW II for a heavy bomb for better accuracy but it did not work in practice. The springs lost tension in storage and the propelling charge sometimes bent or warped the fins leading to instability. British 4.2 was rather famous for this, Damaged fins would lead to the bomb flipping end for end and the bomb would land about 1000 yds short of the target, often it was claimed, in the vicinity of the forward observer.


"The round needs to be of a precise diameter for proper function with a large enough an air gap to allow the shell to easily slide down the tube. When the the round fires, something is needed to seal that gap for maximum performance.
The "bourrelet" feature provides the necessary gas seal. The bourrelet is a series of grooves machined into the wall of the shell body. When the high pressure propellant gas begins to pass between those grooves and the inner wall of the tube, air turbulence is created in each pocket forming an effective gas-check. Without this grovved feature, range would be significantly reduced due to lost pressure."
From U.S. 60mm and 81mm H.E. Mortar Rounds (WWII) - Inert-Ord.Net
This maybe clearer that what I wrote.
 
Shortround6 said:
The US also used a long bomb but it lost favor during the war. In part because of the decreased range.
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Between 1935 and the ww2, all the armies can try out the different mines/bombs of different weights and sizes, and then settle on the most optimum choice. Eg. the long 81mm bomb was Mlle 1931, and weighted 6.8 kg; the short bomb weighted 3.3 kg (weight figures for what the Italians had). Arriving at, say, 5 kg bomb as the sweet spot is not a long shot.

Shortround6 said:
From U.S. 60mm and 81mm H.E. Mortar Rounds (WWII) - Inert-Ord.Net
This maybe clearer that what I wrote.
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Thank you.
 
Not all mortars were the same, The British 3in mortars were just about the worst. British troops loved using captured Italian mortars and using Italian bombs in British barrels, at least until the barrels bulged and base plates bent. Just because they were making a better mortar and bomb in the early 30s than they did in 1918 doesn't mean they should have stopped improving things.
When the Italians have more mortars per battalion and they almost out range the British 3in by about 2 to 1 it means the British need to something else to counter the Italian mortars. Like 25pdr guns.
If you look at the American 81mm mortar on the naval mount it could be either drop fired or trigger fired, but it had to be muzzle loaded ( tip barrel up to at least 30 degrees and drop bomb in the muzzle). You can figure out how to breech load it and you can load at less than 30 degrees but something is going to go up and not just cost.

People knew about bigger mortars. They just weren't quite sure what to do with them. They started needing a lot more transport. With the size of the crews and size of the truck needed and the size/amount of transport needed some armies figured that they should spend the money on artillery. Or at least use large mortars to to equip artillery units and not try to foist them off on the infantry.
 

The 120 mm F1 mortar platoon was removed from the french infantry at the beginning of the 2000s and the mortars transferred to the artillery as dual dotation with the 155 mm guns.

This displeased everybody :

- the infantry lost its pocket artillery and had to rely on 81 mm mortars, or wait until the gentlemen from the artillery to be ready to support them ;

- the artillery did not consider the mortar as serious enough for their corporation.

As the artllery will receive the 120 mm MEPAC (Mortiers embarqué pour l'appui au contact) variant of the multipurpose Griffon, the infantry regiments tracked 120 mm mortar platoons are in the process of being recreated (4 per platoon).
 
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Some people have had a fun way of acknowledging the existence of the bigger mortars, and indeed didn't know what to to do with them. Like the Germans, that saw the bigger mortars as something that is there to lay the smoke (and possibly the nastier chemicals, if it comes to blows?), and their bigger mortars were not that convincing. They saw the fault of their ways and adopted the Soviet 120mm mortar - that was actually Brandt's design manufactured under licence.
Both UK and USA were in the similar camp with the Germans, all of them introduced the HE ammo for their 105-110 mm mortars years after the respective mortars were introduced.

Some people were missing the mark with the small mortars, too. The German 5cm was 3 times heavier than the British counterpart. Italians flunked badly with the Brixia 45mm.
 
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