(Multi-)national weapon/ammunition standards without the Fall of France?

[Elan Vital]

Hi everyone,

A very broad subject in which opinions may vary.

Historically, the Fall of France was a very significant point of divergence in WW2 which left Germany free to expand the war in other theaters and inspired Italy to enter the war.
Countries which may have remained neutral or been part of secondary theaters (Italy, the Balkans, Hungary, USSR which may have grabbed territory when convenient), had the Germans been fixed by the Entente in French or Benelux territory, instead became part of a mechanism which led to the destruction of much of the pre-1940 European military-industrial complexes and part of them would end up under Soviet control.

The destruction of these existing or burgeoning complexes and the rise of the USA and USSR as the primary providers of weapons in new military blocs facilitated the creation of international weapon or ammunition standards, such as 7.62x51 and 5.56x45 in the West, or 7.62x54 and x39 and 5.45mm in the East.

So, for the sake of imagination, I posit this scenario: France never falls, and Germany is eventually defeated by the Entente. Italy is sufficiently deterred to remain neutral, even in the Balkans. If the war expands to the Balkans (Germany seeking to obtain more critical ressources or the Entente convincing neutral countries to get involved), the limited forces available on either side prevents the fall of any Balkan country or the complete destruction of its military industry. Hungary, Finland and Bulgaria remain neutral. The USSR stays neutral, or at most grabs the Baltics, Poland, Czechoslovakia and possibly parts of Germany in opportunistic late-war moves. The USA could continue purveying weapons to the Entente and neutrals, assuming it doesn't feel compelled to fight in Europe. What happens in Asia is left to the poster's opinion.

What ammunition or weapon standards could remain or emerge in the years and decades following this alt-WW2?

France's military industry would have been in continuous operation. Neutral Italy wouldn't have suffered any of the weapon production restrictions its historical counterpart briefly got after WW2. The limited, but existing industries and stockpiles of European minors stay in place.

The USA, while a major purveyor of weapons, would face competition in Europe and would probably have produced a much smaller surplus of cheap weapons to hand out.

Complex systems like aircrafts, armored vehicles would be difficult to anticipate with such a major point of divergence beyond the first few years.
But notably, the French had been sending R35 light tanks and 25mm AT guns as aid in 1939-40 to Romania, Yugoslavia and Turkey, and could maintain and even expand such aid protocols to the Balkans and Turkey into 1943, with those serving in the 1940's and possibly 50's as reserve equipment.

For ammo, the French historically kept 7.5mm for quite some time and here would have even larger stocks of this ammo and weapons to use it. Italy suspended 7.35mm weapon issuance in 1939, but might reintroduce a modern cartridge as the situation gets clearer. 30.06 may not be as common in Europe, so 7.62 NATO may not happen in its historical form and fielding. 7.92 Mauser was relatively common in minor European countries?

 

[ArtosStark]

Interesting.

For one thing one of the early drivers towards intermediate cartridges was the German development of the StG 44 in Germany. A different war could mean this does not happen which may delay the switch to intermediate cartridges.

In addition some of the driver for early post war firearms was the perceived need to combine the roles of the rifle and sub machine gun to better accommodate the use of troops getting in and out of vehicles. A war stopped in France could, at least for a fair amount of time, have more similarities to a Great War static conflict. So that driver may be weaker. Though I suppose the concept would still have value in a trench setting and there would have likely been an extended mobile phase at some point.

The question then is, would the armies of Europe be looking for more efficient full power cartridges in the immediate aftermath of the war, as happened with the 7.62 NATO due to US preference, or are they looking at early intermediate cartridges?

If it’s the former, I suspect the beat option is 7.92 Mauser. It is well known among many of the smaller militaries, pretty widely available commercially and was the preferred replacement for the British (whose need to update the .303 meant they spent a fair bit of time on the issue) prior to the StG 44 being analyzed. The main stumbling blocks would likely be the Americans and the French. The US will very likely always want their own cartridge. But they may not have the heft in this scenario to force it on the other members and may just go their own way. France, meanwhile, has what I think is a serviceable cartridge in the 7.5 mm in large amounts. And they would be a key part of any attempt to standardize, so that carries weight. Maybe everyone ends up compromising on a new cartridge developed to try and meet their requirements?

If the shift to intermediates is not delayed by the US desire for a longer range rifle cartridge, then we are looking at a brand new cartridge. Probably in the 6-6.5 mm range as the original British preferences showed before the desire to try and meet US preferences led to the increased size and power .280.

 

[Dilandu]

The USSR stays neutral, or at most grabs the Baltics, Poland, Czechoslovakia and possibly parts of Germany in opportunistic late-war moves.

USSR would likely enter the war at circa 1942; the Red Army would be re-armed and combat-ready, and French army would also be ready to start offensive. So the most likely scenario is USSR entering the war in 1942, coordinating (more or less) with Allies command to launch a two-fron assault against Germany.

 

[MadRat]

7.62 x 51 mm was the .308, so it will still happen. The .30-06 (.308 bullet in 7.8 x 63.3 mm cartridge) was considered too heavy by WW2. The American Army did steer towards .264 caliber (7.22 x 51 mm) but this was a radical and ultimately dead end. The .308 was a good compromise.

5.56 x 45 mm might not. Without WW2 experience there is no NATO.

 

[Elan Vital]

Interesting.

For one thing one of the early drivers towards intermediate cartridges was the German development of the StG 44 in Germany. A different war could mean this does not happen which may delay the switch to intermediate cartridges.

In addition some of the driver for early post war firearms was the perceived need to combine the roles of the rifle and sub machine gun to better accommodate the use of troops getting in and out of vehicles. A war stopped in France could, at least for a fair amount of time, have more similarities to a Great War static conflict. So that driver may be weaker. Though I suppose the concept would still have value in a trench setting and there would have likely been an extended mobile phase at some point.

The question then is, would the armies of Europe be looking for more efficient full power cartridges in the immediate aftermath of the war, as happened with the 7.62 NATO due to US preference, or are they looking at early intermediate cartridges?

If it’s the former, I suspect the beat option is 7.92 Mauser. It is well known among many of the smaller militaries, pretty widely available commercially and was the preferred replacement for the British (whose need to update the .303 meant they spent a fair bit of time on the issue) prior to the StG 44 being analyzed. The main stumbling blocks would likely be the Americans and the French. The US will very likely always want their own cartridge. But they may not have the heft in this scenario to force it on the other members and may just go their own way. France, meanwhile, has what I think is a serviceable cartridge in the 7.5 mm in large amounts. And they would be a key part of any attempt to standardize, so that carries weight. Maybe everyone ends up compromising on a new cartridge developed to try and meet their requirements?

If the shift to intermediates is not delayed by the US desire for a longer range rifle cartridge, then we are looking at a brand new cartridge. Probably in the 6-6.5 mm range as the original British preferences showed before the desire to try and meet US preferences led to the increased size and power .280.

I suspect that the war could last into 1942 if not even 1943 or 1944 as the Allies did not expect numeric nor massive material superiority in the 1941 campaign season. At that point, the Germans might have some of their historical 1942 prototype intermediate cartridges and assault rifles that the Allies could find at the end of the war.

If I recall, weren't the British still expecting to standardize on 7.92 Mauser after the war as of 1942-44? Considering that this was a common cartridge in Europe, if the British commit to it, we may see 7.92 Mauser in service for some time in non-French/Italian/Soviet Europe.

As of 1940, the French had been contemplating a new machinegun cartridge centered around 8mm Mle 32N bullet in a modern cylindrical case for the successor to the 8mm Hotchkiss, as some time would be needed to develop the new MG anyway (previous protos lacked the desired belt feed) and they were concerned about 7.5mm being a little light for medium machineguns. Possibly they may commit to it, in which case the French would maintain a 2-tier system with 7.5mm for light small arms and modern 8mm for MGs.

USSR would likely enter the war at circa 1942; the Red Army would be re-armed and combat-ready, and French army would also be ready to start offensive. So the most likely scenario is USSR entering the war in 1942, coordinating (more or less) with Allies command to launch a two-fron assault against Germany.

The timing for cobelligerency sounds about right.

 

[zen]

It all depends and right down to rifle ammunition if not to pistol, options existed.
Prior to WWII UK was looking at another high pressure smaller diameter bullet to that of the earlier pre-WWI type.
But not just that, as interest in the Toggle locking rifle system from the US using .276.

France at wars start might have a variety of options and that includes a similar 8mm intermediate round from the end of WWI which could parallel German developments.

 

[Archibald]

A pretty awesome TL
https://www.alternatehistory.com/forum/threads/a-blunted-sickle-thread-ii.402994/

 

[Scott Kenny]

If the shift to intermediates is not delayed by the US desire for a longer range rifle cartridge, then we are looking at a brand new cartridge. Probably in the 6-6.5 mm range as the original British preferences showed before the desire to try and meet US preferences led to the increased size and power .280.

No, the British Optimum was .277"-.284" projectiles, 130-140gr at 2500fps.

The two previous attempts to replace .303 were both .277" projectiles. .276 Enfield and .276 Pedersen.

7.62 x 51 mm was the .308, so it will still happen. The .30-06 (.308 bullet in 7.8 x 63.3 mm cartridge) was considered too heavy by WW2. The American Army did steer towards .264 caliber (7.22 x 51 mm) but this was a radical and ultimately dead end. The .308 was a good compromise.

7.62x51 was literally loaded to the same power levels as M2 ball .30-06. 150gr at 2800fps. It was too much for automatic rifles in WW2, it was too much for automatic rifles after WW2.

It's arguably pretty good for machine guns, but I'm not sure it's enough better than 7x43mm to make it worthwhile to have a separate MG caliber from the rifle caliber. Or at least not if the MG caliber is 7.62mm. Some long-for-caliber 7.92mm might work a lot better. 250-300gr, not 200gr.

5.56 x 45 mm might not. Without WW2 experience there is no NATO.

At least the US would not be the dominant power in NATO.

 

[MadRat]

7.62x51 was literally loaded to the same power levels as M2 ball .30-06. 150gr at 2800fps. It was too much for automatic rifles in WW2, it was too much for automatic rifles after WW2.

Different propellants between them which you expect with 40 or so years of technology progress. .30-06 was still around 3.5% better with the 150 grain bullet and enjoyed some longer range because of about 100 fps advantage. The M2 was not as good as ammunition from other countries but met the needs of the U.S. Army. You could obviously carry more 7.62 x 51 mm ammunition compared to .30-06 (7.8 x 63.3 mm). The 5.56 x 45 mm enjoyed a similar drop in performance for the exchange of a significantly larger edge in carried ammunition. Progress is not always better performance but it generally is close enough to not matter as the sheer number of additional rounds available more than makes up the difference.

 

[Scott Kenny]

Different propellants between them which you expect with 40 or so years of technology progress. .30-06 was still around 3.5% better with the 150 grain bullet and enjoyed some longer range because of about 100 fps advantage.

When the .30-06 was loaded with the same powders as 7.62, yes.

But 7.62x51 was specified to have the same 150gr bullet at 2800fps that the old M2 ball .30-06 made. That was literally the design brief. "Make .30-06 power but with a shorter case"

The 5.56 x 45 mm enjoyed a similar drop in performance for the exchange of a significantly larger edge in carried ammunition. Progress is not always better performance but it generally is close enough to not matter as the sheer number of additional rounds available more than makes up the difference.

We can make arguments about 5.56.

IMO the USAF Security Police would have still adopted the 5.56 as the thing to replace their old M2 Carbines. As GAU-5Ps, not as M16s. But without the US getting into Vietnam, I don't think that there would have been a collapse of the "infantry gets rifles, everyone else gets carbines" model that came with the M16s.

I think the US would have eventually been persuaded to load something comparable to 7.62x39. More power than .30 carbine so it's effective out to 300m or so. Possibly using the same 7.62mm bore, for the same reasons the Germans used 7.92mm and the Soviets used 7.62mm.

If we successfully get rid of LtCol Rene Studets from OrdBu, then the US might be persuadable to adopt something like the 7x43mm, since that's got better effective range than x39.

 

[ArtosStark]

No, the British Optimum was .277"-.284" projectiles, 130-140gr at 2500fps.

The two previous attempts to replace .303 were both .277" projectiles. .276 Enfield and .276 Pedersen.

That’s what was developed for the EM-2, yes but not what was initially preferred. Once the idea of intermediate cartridges came about the British arms committee determined that the ideal size was 6-6.5 mm. The same people would later develop a 6.25mm round a few years later that was considered for adoption before requirements changed. But they also knew from the start that they were unlikely to get it adopted by the British government if they couldn’t get the US on board and that they would t get the US on board unless they could try to play to the desire for something more powerful. So they instead compromised on making rounds between .270 and .280. Over time they kept moving to the higher end for size and power, dropping the smaller options and adjusting the larger for more powerful, always chasing the US board.

If the U.S. desire for a .30-06 in smaller package is not as critical to adoption its possible that the original ideas of 6-6.5mm would find more acceptance with the other NATO members.

 

[A Tentative Fleet Plan]

I wonder if we might see Anglo-French standardisation on 7.5×54mm? Throughout the Second World War, Britain was seeking to standardise on a new rimless cartridge, and considered both German 7.92×57mm and American .30-06/7.62×63mm, and designed prototype self-loading rifles chambered in both rounds.

Without the Fall of France forcing Britain to purchase American small arms for the Home Guard, and US entry and into the war and consequent economic mobilisation and glut of .30-06 weapons, it's unlikely that said round would be considered.

7.92mm does have some argument for it, it after all already being manufactured in Britain for the Besa, but given that prior to the Fall of France both Britain and France were planning to standardise on FN Brownings chambered in 13.2×99mm Hotchkiss as aircraft machine guns, that opens up the possibility of Britain adopting another French cartridge?

 

[Scott Kenny]

About the lightest round you'd want to standardize your infantry rifles on would be equivalent to 6.5 Arisaka. With the caveat that 6.5 Arisaka is kinda lousy as an MMG round, hence why the Japanese either copied .303 (IJN) or made a rimless clone of .303 (IJA). So now you need to convince the Generals to allow the MMGs to use different ammunition than the infantry rifles and the light MGs.

Throughout the Second World War, Britain was seeking to standardise on a new rimless cartridge, and considered both German 7.92×57mm and American .30-06/7.62×63mm, and designed prototype self-loading rifles chambered in both rounds.

Even before WW1 Britain was trying to get rid of the .303. Pattern 1913 Enfield in .276 Enfield (7x60mm RB) immediately prior to WW1 kicking off, then strongly considering co-production of Pedersen rifles in .276 Pedersen (7x51mm) in the 1930s. Except that the US didn't buy Pedersen rifles.

I really wish Garand had told MacArthur that his automatic rifle couldn't be chambered in .30-06 and that the best way to handle Congress was to tell them that all the .30-06 was now machine gun ammunition.​

7.92mm does have some argument for it, it after all already being manufactured in Britain for the Besa, but given that prior to the Fall of France both Britain and France were planning to standardise on FN Brownings chambered in 13.2×99mm Hotchkiss as aircraft machine guns, that opens up the possibility of Britain adopting [7.5×54mm]?

Maybe?

But then you're looking at changing weapons calibers in the lead up to a war and that's messy at best.

Your best option would be to keep the old .303 barrels for machine guns and rechamber Brens and infantry rifles for the new cartridge. Then rebarrel the Maxim/Vickers guns once you've burned up all the .303. ​

If Britain isn't getting a semi-auto rifle with their common ammunition, they really should keep the old SMLE or No4. That's basically the best fighting rifle design of all the bolt actions. The Mauser is a great hunting rifle, and the Springfield is a great target rifle. But we're not hunting, and we're not at a target range. We're at war.

 

[A Tentative Fleet Plan]

But then you're looking at changing weapons calibers in the lead up to a war and that's messy at best.

Your best option would be to keep the old .303 barrels for machine guns and rechamber Brens and infantry rifles for the new cartridge. Then rebarrel the Maxim/Vickers guns once you've burned up all the .303. ​

If Britain isn't getting a semi-auto rifle with their common ammunition, they really should keep the old SMLE or No4. That's basically the best fighting rifle design of all the bolt actions. The Mauser is a great hunting rifle, and the Springfield is a great target rifle. But we're not hunting, and we're not at a target range. We're at war.

I'm talking about them doing this postwar, after defeating Germany whilst in an alliance with France, in the same way that they considered planning to do it with 7.92 or .30-06 OTL. The planning took place during the Second World War, but they weren't going to implement said plans until the war had been won.

 

[Scott Kenny]

I'm talking about them doing this postwar, after defeating Germany whilst in an alliance with France, in the same way that they considered planning to do it with 7.92 or .30-06 OTL. The planning took place during the Second World War, but they weren't going to implement said plans until the war had been won.

Postwar. How'd I miss that? *facepalm*

I think it'd work. 7.5mm is still big enough to be viable as a GPMG cartridge. The trick is if they'd learn the lesson of the intermediate cartridge in the war. Else I think the British are still going to push for the 7x43mm instead of the full power 7.5x54mm.

But now we're getting a 7x43 FAMAS, and I'm absolutely here for that!

 

[A Tentative Fleet Plan]

Postwar. How'd I miss that? *facepalm*

tbf I don't think I actually explained the full context behind my thinking in my first post.

As part of the section covering the EM-2, this covers some of the thinking of the mid war to early post war period where they looked at adopting 7.92mm and .30-06.

https://kclpure.kcl.ac.uk/portal/en...the-politics-of-rifle-development-1880-to-19/

 

[Elan Vital]

I wonder if we might see Anglo-French standardisation on 7.5×54mm? Throughout the Second World War, Britain was seeking to standardise on a new rimless cartridge, and considered both German 7.92×57mm and American .30-06/7.62×63mm, and designed prototype self-loading rifles chambered in both rounds.

Without the Fall of France forcing Britain to purchase American small arms for the Home Guard, and US entry and into the war and consequent economic mobilisation and glut of .30-06 weapons, it's unlikely that said round would be considered.

7.92mm does have some argument for it, it after all already being manufactured in Britain for the Besa, but given that prior to the Fall of France both Britain and France were planning to standardise on FN Brownings chambered in 13.2×99mm Hotchkiss as aircraft machine guns, that opens up the possibility of Britain adopting another French cartridge?

Postwar. How'd I miss that? *facepalm*

I think it'd work. 7.5mm is still big enough to be viable as a GPMG cartridge. The trick is if they'd learn the lesson of the intermediate cartridge in the war. Else I think the British are still going to push for the 7x43mm instead of the full power 7.5x54mm.

But now we're getting a 7x43 FAMAS, and I'm absolutely here for that!

Given that the French would have just barely completed rearmament to 7.5x54 during the war, they might be reluctant to change calibers in the same timeframe as the historical Anglo-Americans who had much older 30.06 and .303 calibers and thus were less susceptible to sunken cost falacy. And indeed, French efforts to adopt 7.62 NATO were slow historically.

So if there is any standardization in the early 50s, it would make more sense if the British adopt 7.5x54 rather than the French agreeing to an entirely different intermediate cartridge. If the war in Europe ends no later than 1944, the impact of German intermediate cartridges on Allied thinking would be reduced further even if the French and British had both looked into intermediate cartridges independently of the Germans in the interwar period.

However, the MAS-40 that the French intended to introduce in 1941 was preferably going to be the magazine version akin to the MAS-44, and with a proper production line set up, they could definitely skew the MAS 36/40 mix towards the latter after the war or even late in the war. In such a case, would they even bother with MAS 49 and 49/56? A newer gun may be necessary then.

 

[Scott Kenny]

Given that the French would have just barely completed rearmament to 7.5x54 during the war, they might be reluctant to change calibers in the same timeframe as the historical Anglo-Americans who had much older 30.06 and .303 calibers and thus were less susceptible to sunken cost falacy. And indeed, French efforts to adopt 7.62 NATO were slow historically.

Fair point.

So if there is any standardization in the early 50s, it would make more sense if the British adopt 7.5x54 rather than the French agreeing to an entirely different intermediate cartridge.

Thing about various intermediate cartridges is that you do arguably still need a GPMG, even the Soviets kept their .303-equivalent in service for that purpose.

Even the 7x43 would not have made a good GPMG cartridge, despite the 600m capabilities of the round.

Also, the French will likely be replacing their bolt-actions with semi-autos post-war anyways. That's a reasonable time to discuss maybe changing calibers.

So now you can talk to the French about how they're planning on replacing their SMGs and bolt-action rifles. They keep the 7.5x54 for GPMGs and DMRs (the 191gr/12.35g load is very nice for MG/DMR work), but replace all their SMGs and 9/10 rifles per squad with the intermediate cartridge. They get to sort through all their rifles and choose the best shooting to keep as DMRs, surplus off the others. The US will always buy milsurp! And honestly, so will the former French colonies.

Which kinda brings us to the 1980s French military setup, but in the 1950s or 1960s. And the British finally get a new rifle cartridge, maybe buying some of the French rifles for use as DMRs or maybe keeping the Lee-Enfield No4Ts, and can either convert the Vickers MMGs to 7.5 or replace them with probably FN MAGs like they did historically.

If the war in Europe ends no later than 1944, the impact of German intermediate cartridges on Allied thinking would be reduced further even if the French and British had both looked into intermediate cartridges independently of the Germans in the interwar period.

However, the MAS-40 that the French intended to introduce in 1941 was preferably going to be the magazine version akin to the MAS-44, and with a proper production line set up, they could definitely skew the MAS 36/40 mix towards the latter after the war or even late in the war. In such a case, would they even bother with MAS 49 and 49/56? A newer gun may be necessary then.

If the US mostly stayed out of the War in Europe, there's little chance it'd end in 1944, even without the fall of France (let's assume that the Maginot Line was actually completed clear down the Belgian border to the coast, so there's no way around it this time).

 

[A Tentative Fleet Plan]

If the US mostly stayed out of the War in Europe, there's little chance it'd end in 1944, even without the fall of France (let's assume that the Maginot Line was actually completed clear down the Belgian border to the coast, so there's no way around it this time).

You could probably double or triple the levels of funding for the Maginot line, and it's overall length would not increase that much.

There's a pretty extensive list of work that was deferred or cancelled altogether, many artillery and infantry works were downgraded to infantry works (in the case of the artillery works, particularly the eastern end of the Fortified Region of Metz) or even to isolated casemates (in the case of both artillery and infantry works, particularly common across the length of the Fortified Region of Lauter), not to mention the planned ditches flanked by counterscarp casemates for some large artillery works (only partially completed for Hackenburg and Hochwald, but planned for a number of other works), and the planned infantry shelters, built only in a few fortified sectors

And that's the works we have relatively solid plans for. The was a third Fortified Region of Belfort-Haute Alsace planned, which presumably would have rivaled those of Lauter and Metz, and plans for a second line of defences referred to as "barrier positions" for each of the three planned fortified region.

These would consist of the old Imperial German Festen around round Metz, an entirely new line built from scratch running between Saverne and Mutzig, and the old forts of the Séré des Rivières system around Belfort-Lomont for the Fortified Regions of Metz, Lauter and Belfort-Haute Alsace respectively.

And that's just the Old Fronts planned and constructed in the late 1920s and early 1930s, let alone the New Fronts planned after 1934.

 

[Colonial-Marine]

I understand that pre-WW2 the UK wanted to switch from .303 to a rimless caliber but why 7.92mm (8mm Mauser)? Were they considering any "new" calibers instead? For example, pre-WW1 they had been testing the .276 Enfield used by the Pattern 13 rifle.

As for the French I know they were in the process of phasing out the 8mm Lebel with new designs chambered in 7.5x54mm, but I recall reading somewhere they were also considering a higher power caliber specifically for machine guns, similar to what the Swedes had with their 8x63mm cartridge.

USSR would likely enter the war at circa 1942; the Red Army would be re-armed and combat-ready, and French army would also be ready to start offensive. So the most likely scenario is USSR entering the war in 1942, coordinating (more or less) with Allies command to launch a two-fron assault against Germany.

I'm sure Germany and the USSR would end up at war at some point, if it is clear the French are winning, they will probably join in and launch a major offensive, but as long as the outcome is still in question why would they not sit back, supply Germany with some of what they need to keep fighting, and allow two potential foes to weaken each other?

You could probably double or triple the levels of funding for the Maginot line, and it's overall length would not increase that much.

There's a pretty extensive list of work that was deferred or cancelled altogether, many artillery and infantry works were downgraded to infantry works (in the case of the artillery works, particularly the eastern end of the Fortified Region of Metz) or even to isolated casemates (in the case of both artillery and infantry works, particularly common across the length of the Fortified Region of Lauter), not to mention the planned ditches flanked by counterscarp casemates for some large artillery works (only partially completed for Hackenburg and Hochwald, but planned for a number of other works), and the planned infantry shelters, built only in a few fortified sectors

And that's the works we have relatively solid plans for. The was a third Fortified Region of Belfort-Haute Alsace planned, which presumably would have rivaled those of Lauter and Metz, and plans for a second line of defences referred to as "barrier positions" for each of the three planned fortified region.

These would consist of the old Imperial German Festen around round Metz, an entirely new line built from scratch running between Saverne and Mutzig, and the old forts of the Séré design Rivières system around Belfort-Lomont for the Fortified Regions of Metz, Lauter and Belfort-Haute Alsace respectively.

And that's just the Old Fronts planned and constructed in the late 1920s and early 1930s, let alone the New Fronts planned after 1936.

Are there any good sources of information about these planned but unbuilt Maginot line defensive works?

 

[Ainen]

The premise basically saves the 1930s colonial world (at least for a while).
Probably with same powers doing same things as before(doing their own ecosystems).

 

[Scott Kenny]

I understand that pre-WW2 the UK wanted to switch from .303 to a rimless caliber but why 7.92mm (8mm Mauser)?

https://en.wikipedia.org/wiki/Besa_machine_gun

Were they considering any "new" calibers instead? For example, pre-WW1 they had been testing the .276 Enfield used by the Pattern 13 rifle.

They were considering .276 Pedersen between WW1 and WW2, but then the US chose the Garand rifle because it could be built in .30-06 and the UK dropped the project entirely for reasons I'm not sure about.

As for the French I know they were in the process of phasing out the 8mm Lebel with new designs chambered in 7.5x54mm, but I recall reading somewhere they were also considering a higher power caliber specifically for machine guns, similar to what the Swedes had with their 8x63mm cartridge.

Oh? Someone making 338 Lapua in the 1950s would be awesome. Or rather, 338 Norma, since that's better for belt feds.

 

[Elan Vital]

As for the French I know they were in the process of phasing out the 8mm Lebel with new designs chambered in 7.5x54mm, but I recall reading somewhere they were also considering a higher power caliber specifically for machine guns, similar to what the Swedes had with their 8x63mm cartridge.
works?

Oh? Someone making 338 Lapua in the 1950s would be awesome. Or rather, 338 Norma, since that's better for belt feds.

As part of their new machinegun program to replace the Hotchkiss 1914, the French tested both 9x66 and 7.5x54 mag-fed machineguns, with the MAC designs being the best ones selected for further development.

However, the Infantry changed its mind completely on certain aspects in September 1939. The 9mm caliber was rejected as it was no longer sufficient against lightly armored vehicles, was overkill against infantry and required bulky and complicated sights to use its superior ballistics against aircraft. 7.5x54 was good though not quite ideal for the heavy machinegun role.
The Infantry also now required side-loading, preferably using disintegrating link belts, requiring an essentially new design.

The French thus felt that if they were to design a new belt-fed MG, they might as well do it around the optimal bullet, that being the 8mm Mle 1932 N which was in production. But this time with a rimless cartridge, interpolated from 7.5 and 9mm models. No info exists yet on whether studies of such a new weapon started before the Armistice (as of December 1939, the specifications for this new weapon were still requested). The French were confident that the Hotchkiss 1914 could hold out until a new MG entered production, so it is unlikely that they would have mass-produced the mag-fed 7.5mm MAC as a stopgap.

Meanwhile, the 50 MAC 1936 A mag-fed 7.5mm MGs that had been ordered for field troop trials in early 1939 were built and one MG section armed with this model was created on the 22nd of April 1940 at the Infantry and Tanks Practical Gunnery School and moved to the 44th Infantry Division on the 11th of May.
The 2nd section was ready to move on the 15th, waiting for its magazines. The 3rd and 4th sections were expected in the second half of June and the 5th and 6th sections on the second half of July.
These were on Hotchkiss mounts and 50 mounts of the new Alibert type made at the Versailles Proving Grounds were ordered but not yet delivered as of June 25th.

 

[A Tentative Fleet Plan]

Are there any good sources of information about these planned but unbuilt Maginot line defensive works?

Sorry about taking two weeks to answer this question.

I tend to use French language stuff for this subject, I don't really have many books on this subject at the moment, the best single source I have for the Maginot Line as a whole is a copy of the 2009 edition of Philippe Truttmann's La Muraille de France ou la Ligne Maginot, which does cover some unbuilt combat blocks and works, although not necessarily in any detail, plus I own the three currently published volumes (more will be published in the future) of Frédéric Lisch's Mesures eat Démesures de la Ligne Maginot, which primarily reproduces the plans of various individual combat blocks of the Maginot Line (some of which were unbuilt), but is very light on text.

I occasionally use Wikimaginot, although access to articles is limited on two different levels on the basis of whether a user has an account on the site itself, or if they are a paying member of the association (most of the site is still accessible to users without accounts or membership, however many images and documents may be inaccessible)

A fairly common citation for wikimaginot articles is the 5-volume Hommes et Ouvrages de la Ligne Maginot, which may have further details on unbuilt works, but I can't confirm that, since I don't own a copy of any of the five volumes.