Mechanization

Great posts; many thanks, SR6

The Experimental Birch guns used the later 18pdr barrels, breeches and recoil systems and that was in 1925. there were experimental gun carriers in the First World War based on the Big British tanks. The British played with the Birch guns fot 6 years.

the French had built 8 different prototype SP guns by 1919 and the US had built 12 different models by 1922. The Idea was not novel but exact doctrine and technique needed a lot of work.

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I stand corrected wrt. SP guns being a novelty in late 1930s.

an A9 "Stug" doesn't really have the armor to take part in the direct fire battle, the A9 itself didn't have the armor. A10 maybe.

Part of the British resistance to SP guns in the late 30s was not so much cost but mistaken tactical beliefs. Like the tank was invulnerable (even with 30mm or less armor) and so didn't need artillery support to suppress enemy defenses.

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As it was the case, the belligerents will learn the stuff hard way, despite the new (or 'new') hardware. They are cautiously moving in the direction towards an army that is well mechanized, purchasing the stuff that is affordable, while available without much of delays.

The concept is already somewhat proven, what is needed is a "practical" vehicle to carry it to the next step. Small vehicles with limited ammo storage, limited firing arcs (if used with 8-9 degree traverse mounts) limited working room and some what limited cross country performance (step and trench) are NOT needed in any numbers.

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Now, how much fun discussion would we have with, say, 1944 hardware, if I 'gave' the belligerents the best stuff feasible for 1939? So far we have some very informative posts (and other that are not so informative ), with just 2 vehicles 'designed' - unlikely so in case of 'ideal' stuff? Maybe we need a thread that would cover the 'best possible feasible' for different war's years? Maybe a thread covering the prototypes you are mentioning (if it's not already in the ww1 sub forum?); even the gun-armed rhomboid tanks could be called SP guns. French SP guns on Holt chassis are much sorta 'primitive Stug'.

Stug elevated to 20 degrees.
The OP unit needs to mount the standard OP optics (not much of a problem) a small map area, (not much of a problem) and a decent radio set ( a bit more of a problem). The First German OP unit mentioned Sd Fkz 253 actually had thicker armor on the front than the standard half track. It might be better to use the LT chassis rather than go cheap with the "Bren" carrier.

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Looks like the British will have in France, May 1940, (between other) a force consisting of 120 SP guns, 40 ammo carriers and 20 OP units.

take the Birch gun and scale it back. NO anti-aircraft fire and NO 360 degree traverse

The MK VI light tanks speed of 35mph might be a bit much for an SP gun too.

This was on the drawing boards in the US in 1944 as they were not happy with the M7.

M37 SP 105mm

I think the A9 chassis is a good start. Powered by a bus engine (how much cheaper do you want to get?) Getting rid of the rotating turrets ought to make it a bit cheaper too, Somebody once claimed the Stug was about 30% cheaper than the equivalent tank.

here is an interior shot of an M7



Not real sophisticated. But it shows what is needed and what common sense would dictate. Room for ammo and room for the gunners to work.

The German conversion of the MK VI light was both ingenious and desperation. It was done by a Garrison unit on the coast of France. Germany was short of horses and a 6 gun battery of even WW I left over howitzers would suck up 36-48 horses just for the guns. Dropping to 4 horse teams might mean to slow a movement. With the British chassis just sitting in a depot and not much hope of getting anything better why not go for it?

But to base a peacetime purchase or deployment of a number of batteries on such a limited chassis seems like false economy.

The Amercans in the early part of the war tried to but just about every type of gun they had on just about every chassis. Some worked a whole lot better than others.

Tomo, consider the Russian SU-76 and the T-70 tank. The SU-76 was almost 60 cm longer, with an extra road wheel, and about 40cm wider than the T-70. Compared to a MK VI light tank the SU -76 is 88cm longer and 65cm wider.

The Su-76 carried about 60 rounds for the main gun. The gun is offset and according to some sources the traverse is 16 degrees left and 20 degrees right. Much more useful than 4 degrees each way but not as good as 30 degrees each way.

If you want anything approaching a decent SP gun for a 83-88mm gun/howitzer it is going to be around a 15 ton or better vehicle.

If you want anything approaching a decent SP gun for a 83-88mm gun/howitzer it is going to be around a 15 ton or better vehicle.

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I agree. Using a smaller chassis should be considered only as a wartime emergency measure.

Sd.Kfz.165/1 10.5cm SP Howitzer
Achtung Panzer! - Prototypes !
18,000 kg
188 hp engine.
60 rounds of 105mm ammunition.
30mm frontal armor. 14.5mm armor on sides and rear.
.....IMO something like this should be your objective. If you want the option to engage targets with direct fire then armor should be twice as thick. Which will push weight up to about 22 tons.

With the weight going to 22 tons, the 188 hp engine is lacking. It also sucks more fuel. Install the bigger engine to keep the power to weight ratio, the weight goes again up, so we will bulk up the transmission, suspension track-work; the bigger fuel tanks also demand more volume -> the weight goes up again. So before you know it, it's a 30 ton vehicle, akin to Sherman 105mm.

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-- a new chapter --

After the fall of Poland, it was clear to the Army planers that German tank force was something that is ought to be stopped. The AP ammo was issued for the 18 25pdr cannons, while another AFV entered the service, the 2pdr cannon mounted on the 'Bren' carrier. Also the French 25mm ATG was used in such a fashion.
British armor gave a good service during the campaign of 1940, especially during the counterattack around Arras, where only the timely arrival of the Luftwaffe 8,8cm Flak, halftrack mounted, managed to forestall the advance.

After the fall of France, the British Army has undertaken a deep analysis of both their and enemy hardware employment of it. The invasion seemed imminent, so no time was wasted.
Out of German hardware encountered, the most formidable was a version of the Pz-III tank, an assault gun equipped with long 7,5cm cannon (such a vehicle, armed with shorter 7,5cm gun was deemed as less of a danger). Unknown to the British, the longer 7,5cm cannon was an ordnance from the field gun 7,5cm lefk 16nA, and managed to make a notable impression on both infantry and tank units of the B. Army.
One of the AFVs that was seen as a lesser threat was the Pz-I body armed with 47mm cannon, of Czech origin.
Both that one, and the half tracks with 8,8, were judged as an easier target, but only if enough of the artillery fire can be accurately laid on those.

The 18pdr on the LT chassis was found wanting, and the vehicle to be replacing it needed to be of greater size, with enough of room for crew to work, and plenty of ammo to be carried. The 25pdr is to be the weapon, and, if possible, the new 4,5in. One of the experiences from the BoF was that the ammo vehicles were often used to evacuate the wounded soldiers from the fluent front line, so someone proposed that it might be a good idea to use the modified ammo vehicles to carry the soldiers into battle. Sort of a better 'Bren' carrier.
The A9 SP gun was too easy a target, even for the 37mm ATG, and a better protected vehicle is needed. Since the new vehicle is to encounter enemy tanks, up close personal, a gun far better than the 2pdr and 18pdr is needed.

For all of those new, shining toys to make any effect, the Luftwaffe need to be either far away, or sufficiently suppressed. So the SP AAA is to be produced, while the RAF must do it's part in the future.

Uh, Tomo, the "new" 4.5in British artillery piece was a replacement for the 60pdr gun and weighed about 3 times what a 25pdr did, it would need a chassis in the 40-50 ton range unless you resort to the same "chassis" method the US did with the M7 and the M12. M12 carried the gun while the accompanying M30 (same chassis) carried the gun crew and ammunition.

"The 18pdr on the LT chassis was found wanting..." It should have been found wanting on Salisbury Plain and not in combat. The Officer who authorized any purchase of such equipment past the first one or two should serve the rest of his career serving in a weather station in Nepal.

The MK VI light tank was with in a few inches in width and a foot in length of a Bren or Loyd carrier and offered no real advantage in either load carrying or passenger carrying ability even with a new body. Armies tended to dislike (intensely) APCs that would not support the standard infantry squad structure or something close to it. If the "standard squad/section" was ten men then an APC that would hold 10 men (dismounts) was wanted (or maybe nine men). An APC that held 6 men (dismounts) was not wanted as it meant both new squad tactics/drills and much increased confusion in action.

The British 2pdr gets a bad reputation because it was forced to carry on well past it's normal due date. In actual fact it could see off quite well most any German tank until well into 1941. One major failing was it was not provided with decent ammo for a good part of the time. The Muzzle energy of the Germany 37mm with normal AP ammo is 200,000 joules. The German short 50mm gun had 404,000 joules while the 2pdr with AP shot was 392,000 joules and with APCBC shot 382,000 joules. Unfortunately the British do not get the APCBC shot in production until the end of 1942. Please note that APCBC shot/shells were being used in Naval warfare by 1914 so this is not exactly "new stuff". APCBC shot would have gone a looong way in taking out the face hardened German tanks in 1941-42. Need to actually issue HE ammo has been gone over before. British 2pdr HE ammo, when it did show up, carried about 2 1/2 times the explosive of a German 37mm tank HE shell.

18pdrs as AT armament is nothing short of desperation. AP shot was made and issued but much more in the line of self defense. The effective range is short (much shorter than the 2pdr) and rate of fire (and more importantly, the rate of engagment))is much lower.

There is a lot of controversy about when the 6pdr should have been introduced but the 2pdr could have been much more effective in 1940-41 with different projectiles even without going to new types like APCR or APDS.

These are not mechanization issues as such but changing the chassis under the guns or using (misusing?) odd ball guns on new chassis isn't really going to change things much.

Uh, Tomo, the "new" 4.5in British artillery piece was a replacement for the 60pdr gun and weighed about 3 times what a 25pdr did, it would need a chassis in the 40-50 ton range unless you resort to the same "chassis" method the US did with the M7 and the M12. M12 carried the gun while the accompanying M30 (same chassis) carried the gun crew and ammunition.

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No quarrels here, the 4,5in will NOT share the same chassis as the new SP 25pdr

"The 18pdr on the LT chassis was found wanting..." It should have been found wanting on Salisbury Plain and not in combat. The Officer who authorized any purchase of such equipment past the first one or two should serve the rest of his career serving in a weather station in Nepal.

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He is going to Malaya

The MK VI light tank was with in a few inches in width and a foot in length of a Bren or Loyd carrier and offered no real advantage in either load carrying or passenger carrying ability even with a new body. Armies tended to dislike (intensely) APCs that would not support the standard infantry squad structure or something close to it. If the "standard squad/section" was ten men then an APC that would hold 10 men (dismounts) was wanted (or maybe nine men). An APC that held 6 men (dismounts) was not wanted as it meant both new squad tactics/drills and much increased confusion in action.

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The ammo carrier based APC will look slightly different than the ammo carrier itself.

The British 2pdr gets a bad reputation because it was forced to carry on well past it's normal due date. In actual fact it could see off quite well most any German tank until well into 1941. One major failing was it was not provided with decent ammo for a good part of the time. The Muzzle energy of the Germany 37mm with normal AP ammo is 200,000 joules. The German short 50mm gun had 404,000 joules while the 2pdr with AP shot was 392,000 joules and with APCBC shot 382,000 joules. Unfortunately the British do not get the APCBC shot in production until the end of 1942. Please note that APCBC shot/shells were being used in Naval warfare by 1914 so this is not exactly "new stuff". APCBC shot would have gone a looong way in taking out the face hardened German tanks in 1941-42. Need to actually issue HE ammo has been gone over before. British 2pdr HE ammo, when it did show up, carried about 2 1/2 times the explosive of a German 37mm tank HE shell.

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Thanks for sharing that.

18pdrs as AT armament is nothing short of desperation. AP shot was made and issued but much more in the line of self defense. The effective range is short (much shorter than the 2pdr) and rate of fire (and more importantly, the rate of engagment))is much lower.

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Yep, more of 'we will encounter them, so let's be prepared' stuff, than something active 'let's hunt the panzers'.

There is a lot of controversy about when the 6pdr should have been introduced but the 2pdr could have been much more effective in 1940-41 with different projectiles even without going to new types like APCR or APDS.

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Easy to agree on that.

These are not mechanization issues as such but changing the chassis under the guns or using (misusing?) odd ball guns on new chassis isn't really going to change things much.

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The Brits would made a better show further on, but so will the others

For your consideration:

MK VI AA tanks.





A Vickers 6 ton AA vehicle:



A Vickers 6 ton artillery tractor also known as a Dragon:



And a model of a 40mm on a truck, notice the jack stands:

Thanks for the contribution. Currently I'm working, flat out, so my posts in this thread would be postponed, maybe until September.

We will miss you. take care of your self and your family. Hope the work goes well.

Thanks for the wishes, we're all okay (and expecting a new family member ). The work is really awesome this year.
I'll be able to spare a half an hour daily to check out the forum; you won't get rid of me so easlily