German artillery what-if: going all-in with gun-howitzers past 1935

[tomo pauk]

... ie. artillery pieces that have the barrel length of some 30-35 calibers. Granted, this is a bit longer barrel than on the pieces that can be called like that. like the Soviet ML20, or the British 25 pdr, but bear with me for the duration of this thread. Artillery 'niches' are of 88 mm, 105 mm, 127/128mm, 150mm, and 170mm, with MV of some 650-700 m/s maximum. Max elevation is still above 45 degrees.
The 'no free lunch' rule will be evident - for the same weight vs. the howitzers, shell weight is going to be lighter, but the range will be longer, and so will be the ability to hit the moving targets that come in close, talk to about 1000m. Lets stipulate that Heer has no problems in specifying the 88 gun-howitzer as the backbone of their artillery park instead of the 105 mm howitzer (this is the hardest part probably, since the 105m shell was at least 50% heavier, even if that howitzer was short - if not very short - ranged). Or, go with 105mm gun-how for the motorized or mechanized divisions, and 88mm for the non-motorized units?
The dedicated guns are still being made, like the AT guns, or the long-range guns. They look at piggy-backing on the KM and LW guns for the long-barreled pieces, in order to save time and coin.

Will the Heer artillery park will be better off, or worse off?

 

[Shortround6]

Germans had 4-6 different 10.5cm howitzers with longer barrels (or at least longer range) than the standard le FH 18.
I am not sure where the crossover point is. They got one to have a range of 15km.
But you have the 10.5cm K 18 cannon with a range of 19.075km.
Problem is that they started to gain weight fairly fast although not so bad as the 10.5cm K 18.
The Prototype 10.5cm le K 41 did range to the 15km but it weighed 2640kg instead of 1985kg for the 'standard' Howitzer. Granted this is about 1/2 the weight of the 10.5cm K 18.
Germans thought it was too much gun for the shell weight.
Germans got another 1.65km out of the standard howitzer by using a special shell, a special charge and a muzzle brake.

A lot of people's howitzers maxed out at about 45 degrees of elevation. The US was something of an exception (not the only one). The actual need to fire at higher elevations mostly solved by using more intermediate charges. A shell falling at 60 degrees may very well have been fired at 45 degrees or a bit less. And the poor gunners had been digging in the trails for higher elevation since the days of muzzle loaders. Yes, simply turning the elevation wheel is a lot easier but the resulting gun is often heavier, higher off the ground and costs more.


The British built a very good 88mm gun howitzer and then shot it one wheel, the trail and the elevation system with the crappy ammo.

There are real problems with trying to use large heavy artillery pieces as AT guns. The 10.5cm K 18 fired a 15.56kg AP shell at 827mps which is sufficient to take out just about anybody's tank. Problems include you now have your divisional (or Corp) artillery on the front line and can be taken out by machine gun fire or 81-82mm mortars.
They are useless for using as general support artillery because the first round fired revels the position to any enemy within several km.
With the weight of the barrels they tend to track moving targets both slowly and they tend to overrun the target when the target stops.

As a general rule of thumb for anti-tank work you get a point blank range equal to the Muzzle velocity + 10%.
Now special sights can help out with this (a lot) but now you are spending money on sights that hopefully will never be used on general field gun (if your artillery which is supposed to be 4-6km behind the lines are shooting at enemy tanks the general situation has fallen in the toilet).

High velocity also means high barrel wear but this can be solved by using lighter charges for the shorter ranges as was done by just about everybody's normal howitzers.

A lot of gun companies had offered 75mm/100-105 combos (same carriage and recoil system) between WW I and WW II. Sometimes they needed a little fiddling with the gas pressure in the recoil system but the idea was a cheaper total buy and fewer spare parts needed. They tried selling the idea of swapping the barrels in and out to suit the target/range but that was not really practical.

The Germans did use the same carriages for some different guns. Like the 10.5cm K 18 and the 15cm FH 18 (and others).
The British used the same carriage for the 4.5in gun and the 5.5in gun/howitzer.
The US used the same carriage for the 4.5in gun and the 155mm howitzer.
In all three cases the smaller caliber gun/s fell out of favor as while the extra range was useful, the much lower destructive power for the amount of effort needed to transport and emplace them outweighed the extra range.
British also solved part of the range problem with the 5.5 by finally getting their heads out of their bums and getting a decent shell. The 80lb shell offered almost 1900yds more max range (almost 1/2 the difference between the 4.5 and the 5.5) and the 80lb shell held more explosive than the 100lb shell.

With artillery the weapon is the shell. The gun is just the launcher. Much like bomber aircraft, the weapon is the bomb/s. The bomber aircraft is just the deliver system.

 

[ThomasP]

What Shortround6 said , particularly in relations to the shell being the weapon.

Plus, the consideration that ideally you want to be able to outrange the enemy for the most part.

A paper exercise would be to use something like the US artillery establishment, and use the guns below for both sides:

75mm howitzer
105mm howitzer
155mm howitzer
103mm howitzer

No advantage to either side.

Then give side A gun/howitzers and side A now outranges side B.

Advantage to side A, particularly if side A is on the offense?

As Shortround6 said the weapon is the shell, but if we use the bomber analogy then the bomber has to have enough range to reach the target, as does the artillery piece. If you can hit the enemy at significantly longer range there is (I think) a clear advantage, even with reduced rates of fire and/or individual shell effect.

However, if you are on the defense, the balance changes (maybe?) in favor of rate of fire and/or individual shell effect.

Conventional impact or time fuzed ammunition vs proximity fuzed ammunition is an extreme example of the individual shell effect, as well as the outranged effect - ie with everything else being equal - if you are outranged by the enemy the your proximity fuzed shells do not matter as much unless you are on the defense. If you have the same range then the proximity fuzed shells can be devastating. And if you outrange the enemy and also have proximity fuzed shells then you have clear artillery superiority.

Maybe?

 

[tomo pauk]

Germans had 4-6 different 10.5cm howitzers with longer barrels (or at least longer range) than the standard le FH 18.
I am not sure where the crossover point is. They got one to have a range of 15km.
But you have the 10.5cm K 18 cannon with a range of 19.075km.
Problem is that they started to gain weight fairly fast although not so bad as the 10.5cm K 18.
The Prototype 10.5cm le K 41 did range to the 15km but it weighed 2640kg instead of 1985kg for the 'standard' Howitzer. Granted this is about 1/2 the weight of the 10.5cm K 18.
Germans thought it was too much gun for the shell weight.
Germans got another 1.65km out of the standard howitzer by using a special shell, a special charge and a muzzle brake.

Note that I'm willing to sacrifice the LR weapons on the altar of gun-howitzers, so the 105mm cannon is looked with even lower enthusiasm.

There are real problems with trying to use large heavy artillery pieces as AT guns. The 10.5cm K 18 fired a 15.56kg AP shell at 827mps which is sufficient to take out just about anybody's tank. Problems include you now have your divisional (or Corp) artillery on the front line and can be taken out by machine gun fire or 81-82mm mortars.
They are useless for using as general support artillery because the first round fired revels the position to any enemy within several km.
With the weight of the barrels they tend to track moving targets both slowly and they tend to overrun the target when the target stops.

I'm loathe to use the 5-6 ton towed guns as AT guns, apart the need of self defense.
The 88mm gun-how firing the AP shot at close to 700 m/s will deal with anything, bar later Churchill, KV and IS tanks anyway. HVAP shots can help out from 1941 on. The 105mm gun-how should improve the game further, ditto for the 127-128mm gun-how.

With artillery the weapon is the shell. The gun is just the launcher. Much like bomber aircraft, the weapon is the bomb/s. The bomber aircraft is just the deliver system.

Agreed.
A lot depends on the launcher, or on the delivery system, though.

 

[Shortround6]

Note that I'm willing to sacrifice the LR weapons on the altar of gun-howitzers, so the 105mm cannon is looked with even lower enthusiasm.

The German 10.5 cannon used the same carriage as the 15cm how so they saved a bit of money there. It might have been a bit heavy but tailoring a specific carriage for it might have been a bit much.
The question/s are how much weight you can save going to a lower velocity gun and how much range you have to give up.
Or how much bigger a truck or tractor/halftrack you need to tow it.
The standard Howitzer could be handled with a single horse team although they cheated by using a second team/wagon to cart the ammo. Where the 10.5cm gun howitzer falls???
An opening for the 8.8cm?

I'm loathe to use the 5-6 ton towed guns as AT guns, apart the need of self defense.

Yes, once AT guns went beyond 2 tons things got more than a little weird. Germans had mixed feelings about the 1.5ton 7.5cm PAK 40. It did the job, but it was hard to move.

The 88mm gun-how firing the AP shot at close to 700 m/s will deal with anything, bar later Churchill, KV and IS tanks anyway

This comes to the point of the matter. The British 25pdr (88mm) used a 20lb AP shot (solid) at about 610m/s. The gun weighed just under 4000lbs (2 short tons) and it was a crappy AT gun.
It was too tall, (in order to get the elevation needed) and it had 4 degrees of traverse without using the "wheel" and even that slowed down large changes in traverse. They got 70m of penetration at 400yds at 0 degrees impact. They also needed a supercharge and a muzzle brake to keep the recoil in check. Changing to a split trail carriage might mean several hundred pounds. British did not use horse traction in WW II.

Trying to use a 10.5cm gun firing a 33lb (15kg) shell at 700m/s means a much, much larger gun than the standard 10.5cm howitzers in anybody's army.

HVAP shots can help out from 1941 on. The 105mm gun-how should improve the game further, ditto for the 127-128mm gun-how.

Germans are between a rock and a hard place. They ran out of the materials for HVAP shot part way through the war. In fact the Americans were running low. M4 75mm Shermans were very seldom issued HVAP ammo because they thought the Tungsten carbide cores would be better used in the 3in/76mm guns and for a lot of 1944 these longer barreled weapons often had 2-4 rounds at a time. The 75mm gun tanks rarely saw any.
600m/s is a sort of border area on using capped shot vs plain shot and it also depends on the armor target. Face hardened armor often does better against one than the other but homogenous armor often changes the result. This is impact velocity not muzzle velocity. The next big change is around 800m/s (impact?) were even capped shot has a much greater chance of shattering and the need for the TC penetrators becomes more important. Now if you can simply overwhelm the target (Soviet 122mm gun) it doesn't matter if the shot breaks up. You get a big hole and lots of ex armor pieces and pieces of shot flying around inside of the tank making it a really bad day for the crew.

Getting 700m/s velocity out of large guns pushes them a little too far to the "gun" side

French 1917 GPF (also US 1917-1918) 155mm at 735m/s, only 35 degrees elevation and 13,000kg.

British 6in howitzer of 1915.

430m/s. 45 degrees and 3700kg. and 3700kg is no joke if you don't have trucks/tractors.

Please note that they appear to be pulling the howitzer along a narrow gauge rail line so the ballasted area may help with the weapon not sinking into the mud.

 

[z42]

I don't know if more range is worth the cost? Today, in Ukraine, we see that artillery range does seem to be very desirable. But today, there's also satellites, drones, counter-battery radar, and FO teams with small yet powerful radios that can provide targeting information. But during WWII? If most of your artillery shooting is done by firing at targets basically on the front line, yes range can be useful in the sense you can have more batteries spread out over the place firing into any one target, but less so than today.

Then again, if you're happy with a bit shorter range, a very cheap alternative to howitzers are heavy mortars. Soviets used their 120mm heavy mortar extensively (including post-war). Germans had something roughly comparable in the Granatwerfer 42 - Wikipedia . A large number of heavy mortars for the majority of artillery work on the front lines, and then a bunch of somewhat longer-ranged gun-howitzers for 'special' situations demanding longer range could be a pretty potent combination?

Secondly, you have mobility to take into account. Instead of allocating steel to making longer gun barrels and sturdier carriages, maybe use that steel to produce, say, 6x6 trucks for towing those artillery pieces around instead of using horses? That of course gets into the issue of fuel supply, if the Germans magically transform the Wehrmacht into a motorized force, how do they keep it running? Build more (much more?) synthetic fuel plants?

As for AT capability, yes by all means provide a few AP shells for self defense in situations where the excrement has hit the fan, but this should not be particularly high on the list of priorities for designing an artillery system.

Finally, there's artillery doctrine and targeting. The US is generally lauded as having the most efficient targeting system during WWII, able to rapidly shoot with multiple batteries within range, including time of arrival shooting capability. The last one is pretty useful, as after the first shell hits everybody jumps into cover and the efficiency of subsequent shells is greatly diminished. No reason why the Germans couldn't develop a system like this, and crucially it doesn't require massive extra amounts of steel production either.

 

[z42]

Yes, once AT guns went beyond 2 tons things got more than a little weird. Germans had mixed feelings about the 1.5ton 7.5cm PAK 40. It did the job, but it was hard to move.

By the time you need to back up a truck/halftrack or a team of horses to the gun, under fire, to tow it away, you're realistically gonna lose a lot of those guns very fast. For the smaller guns where the crew can move the gun a bit back before hooking up the towing vehicle/horses this is much less of a problem.

The Germans also had a 12.8cm PAK gun late in the war. Imagine having to move that thing around, under fire..

 

[Shortround6]

But during WWII? If most of your artillery shooting is done by firing at targets basically on the front line,

They stopped that by 1915. May depend of definition of front line. By 1915 (and early 1915) the guns were out of sight of what they were shooting at. The guns were behind buildings, woods, ridges, or in deep pits. Sound location was being used and so was flash at night. The problem was communication. Signal flags did not cut it. telegraph/telephone was used. Carrier pigeons were used for back up when the wires were cut.

The US is generally lauded as having the most efficient targeting system during WWII, able to rapidly shoot with multiple batteries within range, including time of arrival shooting capability. The last one is pretty useful, as after the first shell hits everybody jumps into cover and the efficiency of subsequent shells is greatly diminished. No reason why the Germans couldn't develop a system like this, and crucially it doesn't require massive extra amounts of steel production either.

British may have come up this first? Or at least in parallel.
Problem with this system is while it does not require a lot of extra steel production it required vastly increased radio production. The size of the "network" of interconnected observers, gun batteries, headquarters units exceeded the ability of the signal corp to run wires, maintain wires and, at times, pick up wires for reuse. A British Infantry division of 1944 had over 10 times the number of radios that a 1940 division in France had.

Yes the problem of finding, identifying targets more than few miles behind the lines was more difficult in WW II. The increase in big prime movers and SP guns meant that the guns can move much quicker and evade return fire. And in the 1950s they had radar that could track incoming shells back the firing guns. I think they were doing that with mortars at the end of WW II, at least on a trial basis?

 

[z42]

They stopped that by 1915. May depend of definition of front line. By 1915 (and early 1915) the guns were out of sight of what they were shooting at. The guns were behind buildings, woods, ridges, or in deep pits.

I meant shooting at targets that were located on the front line, not that the guns themselves needed to be there.

 

[Shortround6]

British 1908, not wide spread but the idea was there and dated back to 1794. British had used observation balloons in the Boar war.
Communications better than dropped notes took a while.
The artillery branch of most armies had a lot of officers with engineering degrees. Being able to hit the enemy without them being able to hit back was goal that covered generations.
There was a lot of see-sawing back and forth.

 

[Shortround6]

The gun/howitzer idea has gone through several cycles. How practical it was at times may depend on what years.

Leaving the hundreds of years of black powder out of things we may be looking at at least 3 eras.
1890 (?) to the 1920s (?).
Which saw the introduction of "smokeless" powder or nitrocellulose powder, large changes in steel production/fabrication and the development/introduction of recoil systems.

1920s through WW II or early 1950s.
Better steel and gun construction techniques. Better propellent powders which offered the same performance with lower pressures and temperatures.

1950s and later, which saw even more developments in steel, construction techniques and better propellent.

I am sure there have been further developments since then so eras 4 and 5 ?
In any case we are looking at about 130-135 years and it was only 55 years (basically) from 1890 to 1945.

The US 3in tank gun and the 76mm tank can be used to illustrate the changes from the early 1900s to the very early 40s. The US 3in tank gun started out as a 3in coast defense gun in the early 1900s, was detoured to be the basis for a 3in AA gun and the 3in AA gun barrel and ammo was foisted off on the US heavy tank and anti-tank troops with some modifications.
The gun tube was heavy, it needed more space in the chamber than newer guns needed for the same velocity and shell weight. Army came up with the 76mm tank gun which used the same projectiles out of a skinner and lighter tube and they used a chamber of smaller size.
They may have run into problems during that long path the with 3 in gun getting the accuracy they wanted and/or barrel life which may have lead to extra space in the 3in case being filled with wadding.
They used different powder formulation/granulation between the 12.87lb HE round and the 15lb AP round although the weights were similar. 4.56lb to 4.62lbs in the 3 in gun but the 76mm gun used 3.75lbs for both shells.
For comparison the US 105 Howitzer used a max charge of 3.04lbs for the HE round and this was a total of 7 charges in the case connected by twine. A US 105mm AA gun used a 10.56lbs of powder for a MV of 2800 (853m/s) which is much higher than Tomo is suggesting but starts to show the problem Even if the needed charge was only 6lbs you get a really large combustion space once you start taking out some of the zone charges.
US 4.5in gun had two/3 charges for the 55lb shell, the standard M7 charge gave 1820fps/557.5m/s and weighed 7.44lbs and ranged 16,650yds.
There was an M8 supercharge that gave 2,275fps/693m/s and ranged to 21,125yds. This came in two sections and weighed 11.05lbs. It was possible to only load the base section (8.328lbs) for shorter range but it didn't give the regularity and accuracy of the M7 charge. If they tried to use the type of powder in the M7 charge to get higher velocity they exceeded the same working pressure of the gun before they got near the range they wanted.

This is a problem with the gun/howitzer concept. To get into the 600-700m/s area (or higher) and still be able to fire shells at low velocity at high angles for close range work you have a lot of empty space in the chamber which can lead to lack of consistency. The fact that armies could do it in the late 50s or later doesn't mean they could do it in WW II.
A lot of howitzers use short cases and multiple charges to get a variety of different trajectory curves. But for the smaller weapons these came packed in the cartridge case and could be taken out and discarded as needed. Supplying extra charges or supercharges that came separate from the normal cartridge cases was a logistics and safety problem.

Now depending on how much time one has for development and what the state of the propellent industry is in (and the ability of the logistics train to deal with complications) there may be a lot of things you can do (and have been done from the 1950s onward), that may not have been practical in the 1930s or early 40s.

Germans had tried to be a little too avant-garde in the designs of some of their gun carriages in the 1930s. Since they were using horses they tried to lighten the carriages using aluminum in early production for some components. When they had to save the aluminum for the Luftwaffe some of their weapons got heavier and sometimes improved models started to get too heavy to move around easily using horses.

 

[tomo pauk]

The German 10.5 cannon used the same carriage as the 15cm how so they saved a bit of money there. It might have been a bit heavy but tailoring a specific carriage for it might have been a bit much.
The question/s are how much weight you can save going to a lower velocity gun and how much range you have to give up.
Or how much bigger a truck or tractor/halftrack you need to tow it.
The standard Howitzer could be handled with a single horse team although they cheated by using a second team/wagon to cart the ammo. Where the 10.5cm gun howitzer falls???
An opening for the 8.8cm?

An opening for the 8.8cm gun-how might be it's longer range (in-betwen the 25 pdr and the D44 that did 790 m/s with HE shell - presumably on reduced charge?), on a weapon that weights within a few % of what the leFh 18 weighted. In similar vein, the longer range of 127-128 mm gun-how has an range advantage over the 15cm sFh.
105mm gun-how , with the 8.8 + 128mm combo being favored, probably has not too much of appeal.

This comes to the point of the matter. The British 25pdr (88mm) used a 20lb AP shot (solid) at about 610m/s. The gun weighed just under 4000lbs (2 short tons) and it was a crappy AT gun.
It was too tall, (in order to get the elevation needed) and it had 4 degrees of traverse without using the "wheel" and even that slowed down large changes in traverse. They got 70m of penetration at 400yds at 0 degrees impact. They also needed a supercharge and a muzzle brake to keep the recoil in check. Changing to a split trail carriage might mean several hundred pounds. British did not use horse traction in WW II.

Trying to use a 10.5cm gun firing a 33lb (15kg) shell at 700m/s means a much, much larger gun than the standard 10.5cm howitzers in anybody's army.

As above, the 105mm gun-how will probably see meager production with the aforementioned combo getting most attention.
Soviet 85mm cannon was well under 2000 kg, and was pretty rangy even with low elevation. I'd trade the range (both due to the less powerful shell and shorter barrel) here for elevation.

Germans are between a rock and a hard place. They ran out of the materials for HVAP shot part way through the war. In fact the Americans were running low. M4 75mm Shermans were very seldom issued HVAP ammo because they thought the Tungsten carbide cores would be better used in the 3in/76mm guns and for a lot of 1944 these longer barreled weapons often had 2-4 rounds at a time. The 75mm gun tanks rarely saw any.
600m/s is a sort of border area on using capped shot vs plain shot and it also depends on the armor target. Face hardened armor often does better against one than the other but homogenous armor often changes the result. This is impact velocity not muzzle velocity. The next big change is around 800m/s (impact?) were even capped shot has a much greater chance of shattering and the need for the TC penetrators becomes more important. Now if you can simply overwhelm the target (Soviet 122mm gun) it doesn't matter if the shot breaks up. You get a big hole and lots of ex armor pieces and pieces of shot flying around inside of the tank making it a really bad day for the crew.

Plain AP, HE and HEAT will deal with tanks in a decent fashion, if/when it comes to blows. Especially from the 128mm piece.

Getting 700m/s velocity out of large guns pushes them a little too far to the "gun" side
French 1917 GPF (also US 1917-1918) 155mm at 735m/s, only 35 degrees elevation and 13,000kg.

British 6in howitzer of 1915.
430m/s. 45 degrees and 3700kg. and 3700kg is no joke if you don't have trucks/tractors.

I'm not sure that I've stipulated that Germans must use the ww1 metallurgy for their pieces made in the 1930s.

 

[MikeMeech]

View attachment 796706
British 1908, not wide spread but the idea was there and dated back to 1794. British had used observation balloons in the Boar war.
Communications better than dropped notes took a while.
The artillery branch of most armies had a lot of officers with engineering degrees. Being able to hit the enemy without them being able to hit back was goal that covered generations.
There was a lot of see-sawing back and forth.

Hi
During the 2nd Boer War various signalling methods were used from balloons including a telephone wire within the balloon's steel cable tether, unfortunately this had a habit of breaking, so signal flags were used, including to guns, or as a last resort shouting to people below.
From 1912 there were trials undertaken by the British Army trying to solve the problem of bringing indirect artillery fire onto concealed enemy guns using aeroplane spotting during that year and following years up to the war various signalling methods were suggested and/or tried out. these included dropping messages (that was considered too slow), flags, smoke puffs, lamps, Very lights, smoke bombs as well as wireless (many of these were used during WW1 as primary or secondary signalling methods). The French and Germans used similar signalling methods to solve the same problem.
I have had an article published on this subject 'Communication and Aircraft: The British Military Experience, Pre-First World War Experiments and Practice' in Cross & Cockade International Journal, Winter 2019 Vol. 50/4, for anyone that is interested.

Mike

 

[z42]

I suspect 88mm is a bit on the small side. Most powers seem to have used guns in that size class and below largely as pack howitzers, and of course pressing existing WWI era inventory into service (potentially more or less modernized). The British being the major exception, using the 25pdr as the standard light howitzer (not sure about Japan, so I might be missing whatever it was they did).

In terms of effect on target, for area type targets, there's a benefit of many smaller shells vs fewer larger ones (also why we today have things like cluster munitions), but up until, say, around 15cm or so the effect isn't huge. And bigger shells can, I think, make up for the lesser effect/weight by being relatively cheaper to make, having better range (for the same MV, or equivalently, the same range with lower MV and less issues with barrel wear), probably requiring fewer crew per effect on target. See Effects and Weight of Fire

Post-WWI studies (e.g. Westervelt board in the US) IIRC determined that a range of at least 15 km is desirable. OTOH a range above 20km means that the gun is becoming quite heavy for the punch. So maybe that sort of brackets the target range.

So if we want to improve German artillery by adopting gun-howitzers, what about choosing a single gun (instead of the light + heavy howitzer combos most powers went with for division level fire support)? Max range 15-20km, size determined by the pain threshold in terms of mobility?

Combine this with mass deployment of heavy mortars to replace light howitzers and provide something that is very easily transportable.

So what's the pain threshold in terms of weight? If they are motorized, they can be a lot heavier than if we stipulate they must be effectively movable by horse teams. If the majority of the artillery are the heavy mortars which are easily horse transportable, then allocating trucks for the gun-howitzers might not strain Wehrmacht truck logistics capability too much? Maybe something like the BL 5.5 (with the longer range 80lb shell)? Or even the Soviet ML-20? Or something like the sFH 18 except with a bit longer barrel? Or something smaller, say in the 120-130mm range?

As for when even longer range is required, well for that there's the LW. And railway guns (something that can use normal track, not that Schwerer Gustav monstrosity). Maybe there's enough of a use case for long range heavy corps level guns, like the German 17cm one, but the poor mobility and long setup/teardown times of these are definitely issues.

Of course, as the war progresses, and Germany presses all sorts of captured equipment into service, all this nice logistical simplification goes out the window.

 

[tomo pauk]

So what's the pain threshold in terms of weight? If they are motorized, they can be a lot heavier than if we stipulate they must be effectively movable by horse teams. If the majority of the artillery are the heavy mortars which are easily horse transportable, then allocating trucks for the gun-howitzers might not strain Wehrmacht truck logistics capability too much? Maybe something like the BL 5.5 (with the longer range 80lb shell)? Or even the Soviet ML-20? Or something like the sFH 18 except with a bit longer barrel? Or something smaller, say in the 120-130mm range?

127-128 mm gun howitzer has a nice ring to itself Performance of the post-war D-30, if by a heavier (10%+) weapon?

 

[Shortround6]

I suspect 88mm is a bit on the small side. Most powers seem to have used guns in that size class and below largely as pack howitzers, and of course pressing existing WWI era inventory into service (potentially more or less modernized). The British being the major exception, using the 25pdr as the standard light howitzer (not sure about Japan, so I might be missing whatever it was they did).

Actually most powers, aside from the Germans and US used 75/76mm guns as divisional artillery. The British were the middle ground and then screwed up with the cheap ammo.
Many armies used a mixed armament of 75-76mm field guns and 100-105mm howitzers as the two weapons could use similar/identical carriages. 2-3 batteries of the 75-76mm field guns for each battery of 100-105s.
So everybody had 100-105mm howitzers, but in the Japanese, Italian, French, Soviet armies they were rather outnumbered by the 75-76mm guns. They just don't get much of the glory

So if we want to improve German artillery by adopting gun-howitzers, what about choosing a single gun (instead of the light + heavy howitzer combos most powers went with for division level fire support)?

Se below. Also many armies used 100-105 guns and 150-155 howitzers as corp or even army fire support.

Max range 15-20km, size determined by the pain threshold in terms of mobility?

Here is where things trip and fall down. The increase in range from 15km to 20km takes a lot more gun (and propelling charge) than most people think.
Also the Germans were far from perfect. They did a lot of dumb stuff.
German 10.5cm le FH 18.
Charge 1.........200m/s........3575 meters....................180 grams Ngl Bl P propellent(there were other types of propellent)
Charge 2.........232m/s........4625 meters....................180 grams + 55 grams = 235 grams
Charge 3.........264m/s........5760 meters....................180 grams + 55+60 grams = 295 grams
Charge 4.........317m/s........7600 meters....................180 grams + 55+60+115 = 410 grams
Charge 5.........391m/s........9160 meters....................180 grams + 55+60+115+185 =595 grams
Charge 6.........470m/s.....10,675 meters.................... 200 grams + 784 Grams = 984 grams total.

Now charge 6 was supplied in a separate container and while charges 1-5 came in the cartridge case and were taken out as needed by the gunners, all 5 charges had to be take out and replaced by the two elements of charge 6, ad disposed of or reclaimed ?.
Things got even more 'fun' when they came up with charge 7 and the long range shell used in the 10.5cm le 18M (often had the muzzle brake)
Special charge 540m/s .....12,325 meters................1770 grams
Needed a special shell (more streamlined) and the driving band was moved to the rear (shell was moved forward in the chamber) to make room for the propellent.
Also needed other than the cheapest cartridge cases. Seamed or wrapped cases were forbidden to be used, only drawn cases which means at times the good cases had to be supplied with the special charge.
For 3.44 times the range they had to use 9.83 the amount of propellent.

Germans came up with a number of replacement 10.5mm howitzers/guns but details a bit lacking. They did get to 15,000 meters with 2640kg gun firing at 665m/s. Charge unknown.
The s 10cm K 18 used a three charge system to fire the 15.14kg shell.
Charge 1......................550m/s..............12725 meters.......................2.38kg
Charge 2......................690m/s..............15750 meters.......................2.38kg + 0.91kg = 3.29kg
Charge 3......................835m/s..............19075 meters.......................5.80kg
Charge 3 was another one of the take the charges 1 & 2 out of the case and stuff charge 3 into the case deals.
Note the large amounts of propellent needed it the large chamber. A 15,000 meter gun could have used a lot less propellent but it was till going to be a lot more than the smaller 10.5 guns used to lob their shells 11-12,000 meters. And this meant larger, heavier equipment.
And even if you figure out a 5-7 charge system all of the lower charges are going to need more propellent in the same chambers to get the desired ranges.

Yes by mid war the Germans didn't need (or want?) their 10.5cm howitzers lobbing shells at 3500-5000 meters (within 120mm mortar range) they could probably dispense with with smaller charges and keep the guns out of that particular danger area. But this is well past 1935-39.

 

[tomo pauk]

Of course, as the war progresses, and Germany presses all sorts of captured equipment into service, all this nice logistical simplification goes out the window.

(a bit beyond the scope of the thread, but still
Germany needs to take a look beyond their borders, where the French 75 is fielded by thousands even in the 1930s. Any future war worth speaking about will involve taking it on France or Poland (or both), and it needs to be aggressive, lest Germany is in huge problems. That again means that ammo for that French gun will be captured in many, many thousands.
Hence: design a 75mm gun that can fire French/Polish ammo, while being of a modern design (split carriage etc.) and stressed to fire the more powerful (say, 25% more propellant max) ammo of German design; that German ammo might wreck the French gun thus the future enemy gains nothing with German ammo captured. Couple that with reduction of lower powered 75mm artillery on just 1 ammo type (not 3-4 as it was the case), and keeping the eye on the 75mm AA gun (for the role of a high-end 75mm gun) should the need arises, and Heer has just three 75mm ammo types to procure, instead of 7-8 before 1942 (not counting the 19th century types).

(end OT)

But, that's not all
Germany was making 5 different types of 88mm ammo per T. Williams, with caveat that Tiger and Flak 18 used different primers. The 88x390R round has the properties we might want for the gun-howitzer.

 

[Shortround6]

But, that's not all
Germany was making 5 different types of 88mm ammo per T. Williams, with caveat that Tiger and Flak 18 used different primers. The 88x390R round has the properties we might want for the gun-howitzer.

The British 25pdr case was 292mm long and something in that area would have been good enough, if the Germans were smart enough not burden the poor thing with that idiot 25lb (11.34kg) projectile. In Sept of 1943 the British started work on a new 21lb (9.52kg) shell (better steel) that would range to 14,500yds/13,260m. The new light shell also had the huge benefit of holding 3lbs (1.36kg) of HE instead of 1lb 2oz (510g) like the standard shell. British were still working on it when the war ended.
Germans could have grabbed an 88mm AA shell of 9.4kg ((20.73lbs) that held 870g (1.92lbs) of HE, stuck it in shortened case with a multi charge load and sent it on it's way with about a 1000meter range advantage over the British gun and almost a 3km advantage over the 10.5cm howitzer.
Now if the Germans want to get a little tricky they can make a special howitzer shell with thinner walls and a bit more HE and fire it to just about the same distance, but that does away with the ease of manufacturing/inventory.

For the Germans the further they past the standard 10.5mm Howitzer in weight the more transport problems they have. They didn't like the standard howitzer that much as it was and finally in 1942/43 they came with this assembly of parts.

that was around 200kg lighter and easier to produce than the old standard, it used a lot of 7.5cm AT parts in the carriage.

Heading towards 3000kg guns/weapons in an pretty much horse drawn army was going to give it's own problems.

Germany needs to take a look beyond their borders, where the French 75 is fielded by thousands even in the 1930s. Any future war worth speaking about will involve taking it on France or Poland (or both), and it needs to be aggressive, lest Germany is in huge problems. That again means that ammo for that French gun will be captured in many, many thousands.
Hence: design a 75mm gun that can fire French/Polish ammo, while being of a modern design (split carriage etc.) and stressed to fire the more powerful (say, 25% more propellant max) ammo of German design; that German ammo might wreck the French gun thus the future enemy gains nothing with German ammo captured. Couple that with reduction of lower powered 75mm artillery on just 1 ammo type (not 3-4 as it was the case), and keeping the eye on the 75mm AA gun (for the role of a high-end 75mm gun) should the need arises, and Heer has just three 75mm ammo types to procure, instead of 7-8 before 1942 (not counting the 19th century types).

Germans and French had some rather different ideas of artillery doctrine. There were also a few advances in propellent technology between 1897 and 1917 let alone the mid 1930s.
German 'field' guns used multi charges, 1-3 or 1-4 charges. French (and their clients, including the US) used a single fixed charge.
The French '75' gained almost 50% in range over the years. Mostly due to newer carriages with more elevation and newer shells that did not employ the French ideas of aerodynamics.

Please note that the M4 Sherman tank could fire French 75mm ammo, where it landed compared to where the sights were pointed is subject to question.
The lower charge loads in the multi charge weapons offered different trajectories to the same distances, assuming it was within reach of the lower charge. They caused less wear on the gun bore and less wear and tear on the recoil system and carriage.
If an enemy captures really large stocks of ammo it may be worth while "modifying" it. Like pulling the projectiles, dumping the powder and putting back enough powder to get the ammo to a safe pressure level and then putting the projectiles back and re-crimping. I would note that the Allies put captured German 75mm projectiles into American 75mm cases in North Africa (for M3 grants ?) so this is not totally unheard of.

The Heer, without a really, really ruthless paring of 75mm ammunition types was always going to have a crap load of ammunition types. Unless you also get rid of a number of different guns/gun systems.
Some were specialized like the little infantry howitzers and the mountain guns. Maybe these could have been replaced by mortars but the little rifled weapons were more accurate if point targets were the objective.
The tank guns were always going to be problem because they wanted short ammo to fit in the turrets, at least until you get to the Panther tank with the bigger turret.
Maybe there could have been a little more cooperation between the armored forces and the foot soldiers

 

[tomo pauk]

The British 25pdr case was 292mm long and something in that area would have been good enough, if the Germans were smart enough not burden the poor thing with that idiot 25lb (11.34kg) projectile. In Sept of 1943 the British started work on a new 21lb (9.52kg) shell (better steel) that would range to 14,500yds/13,260m. The new light shell also had the huge benefit of holding 3lbs (1.36kg) of HE instead of 1lb 2oz (510g) like the standard shell. British were still working on it when the war ended.
Germans could have grabbed an 88mm AA shell of 9.4kg ((20.73lbs) that held 870g (1.92lbs) of HE, stuck it in shortened case with a multi charge load and sent it on it's way with about a 1000meter range advantage over the British gun and almost a 3km advantage over the 10.5cm howitzer.
Now if the Germans want to get a little tricky they can make a special howitzer shell with thinner walls and a bit more HE and fire it to just about the same distance, but that does away with the ease of manufacturing/inventory.

Thank you.
I like the off-the-shelf idea better, at least for the 1st years of the gun.

Heading towards 3000kg guns/weapons in an pretty much horse drawn army was going to give it's own problems.

This is why I think that the 10.5cm gun-how is neither here nor there (at least for the ww2 Heer) - will require a substantial prime mover (or even being a SP weapon), while being with a light shell.

The Heer, without a really, really ruthless paring of 75mm ammunition types was always going to have a crap load of ammunition types. Unless you also get rid of a number of different guns/gun systems.
Some were specialized like the little infantry howitzers and the mountain guns. Maybe these could have been replaced by mortars but the little rifled weapons were more accurate if point targets were the objective.
The tank guns were always going to be problem because they wanted short ammo to fit in the turrets, at least until you get to the Panther tank with the bigger turret.
Maybe there could have been a little more cooperation between the armored forces and the foot soldiers

Well, both the infantry, artillery and armored branch need to cooperate and see above the respective turfs - in any fight worth calling it a fight, they are 'in this together'. Even more for the German army, that was big on combined arms.

 

[Shortround6]

Thank you.
I like the off-the-shelf idea better, at least for the 1st years of the gun.

Cutting the existing the 88 x 390 casing down to around 320-330mm might do the trick, about 10% more powder capacity than the British gun and not using a really long barrel.
If you are going to use reduced charges the smaller case means less powder and better uniformity.
The German 7.5cm field guns were not an outstanding bunch in any case. Shells only held about 520g of HE and max range was about 12,300 meters for the best of 4 different versions.
The Pak 40 got an HE round but it used about 30% of the powder charge than the AP round did for a 548m/s velocity, max range about 7700 meters but this was elevation limited.
An 88mm Gun/howitzer adopted in the late 30s might have helped the Germans over the collection of stuff they had.

This is why I think that the 10.5cm gun-how is neither here nor there (at least for the ww2 Heer) - will require a substantial prime mover (or even being a SP weapon), while being with a light shell.

The Problem is going bigger. The Soviet 12.2cm M38 went 2450kg in position but 3100kg in transit and only ranged to 11.8km. The Soviet 12.2cm gun (A-19) fired about 73% further but weighed 2.9 times as much in position. It also has a lower rate of fire.

Adjust as needed for a 12.7/12.8cm weapon.