German logistics, purchase programs and war booty, reality and alternatives 1935-43 (2 Viewers)

[Shortround6]

Indeed. Half track transports would help, such as he Opel Maultier....

There are several points to consider. The 1/2 tracks were a huge advantage in poor weather/bad roads.
On good or even medium roads the advantage disappeared. Most of the Maultier types averaged a max speed of around 40kph. average speed is going to be lower.
Most of the German trucks could max out at 70-85kph depending on model (some were slower) but unless on really good roads they are going to be going slower, just not as slow as the Maultier. The Maultier is going to get bad mileage. Turning the tracks takes more power than making the wheels roll. Some specs say about 1/2- 2/3 the range of the wheeled truck using the same fuel.
Maultier was simple to build. Same driveline and steering of the parent truck.
When you needed a Maultier you needed a Maultier. When you didn't it sucked up fuel, was slow and carried less cargo.
The fancier German 1/2 tracks were rather expensive. They had a much more sophisticated suspension and a much more sophisticated (complex) steering system. For shallow turns the steering wheel just turned the front wheels. For sharp turns the the steering wheel activated track brakes like a tank slowing/stopping the inside track.
The Germans never (rarely?) put a powered front axle on their 1/2 tracks. This hurt some of the mobility/steering. The front wheels tended to plow in bad going.
The fuel mileage of the military 1/2 tracks was not good. The unarmored 3 tonner was supposed to get 240 km using 110 liters of fuel. A 3 ton Opal was supposed to get 320km on 82 liters. Again, when you need the unarmored 3 tonner 1/2 track you need it (towing a 10.5cm howitzer cross country) but for hauling ammo and food on a packed dirt road?
BTW the Ost-schlepper maxed out at just over 17kph. A very interesting and useful vehicle but as a general supply vehicle (large loads over long distance) it sucked.

Logistics is a very, very hard game.

 

[tomo pauk]

Ditch the He100 - it was too small for adequate armament.
Pursue the He112 instead.

He 112 was also small, at least the B version. The early prototypes were trying to beat the Hawker Hurricane in wing thickness and the related drag, as well as being unfriendly towards the mass production.
He 100 with 'normal' cooling should've been able to have a decent firepower, at least a motor cannon + two HMGs, or two cannons like the Bf 109E + two MGs.

Also, when Heinkel demonstrated the He178, get excited and throw the full backing of the RLM behind the fledgling jet program instead of dismissing it as a novelty - and this includes suppressing internal in-fighting.

Greater support for the jet program in general would've made the LW a much tougher nut to crack.

Keep the Hs129, but give it the engine power it needs to perform better. And threaten anyone with a firing squad who mentions installing a BK7.5 on it...

What kind of engine power do you have in mind?

 

[Admiral Beez]

Pursue the He112 instead.

What's your idea for logistics here? Maybe a glider tug like the Bf 109 below carrying a DFS 230?

 

[Shortround6]

He 100 with 'normal' cooling should've been able to have a decent firepower, at least a motor cannon + two HMGs, or two cannons like the Bf 109E + two MGs.

What does an He 100 with 'normal' cooling really bring to the table over the 109F?
Better landing gear/ground handling?

A lot depends on timing and other programs. The MG 131 was running late.
The MG FF and FF/M as a motor cannon never really panned out. Had to wait for the MG 151.

 

[z42]

BoB showed that Germany would have needed a fighter capable of long range escort missions. No, something clunky enough that it gets easily shot down in droves by enemy day fighters like the Bf 110 doesn't cut it. Call it a 'German P-51' if you like, though it doesn't need such extreme range as London->Berlin and back. But say Northern France to Southern England, fight for a good while to protect the bombers, then get back with fuel to spare. Probably not an easy ask for the late 1930'ies to design such a plane, though.

 

[tomo pauk]

What does an He 100 with 'normal' cooling really bring to the table over the 109F?
Better landing gear/ground handling?

Possibility to have more internal fuel, and it might've been had in numbers for the whole 1940. Indeed, the better landing gear.
A few advantages in streamlining, like the smaller and probably a more advanced wing, non-protruding ram air intake, wheel well covers as-is - these can add up neatly.

BoB showed that Germany would have needed a fighter capable of long range escort missions. No, something clunky enough that it gets easily shot down in droves by enemy day fighters like the Bf 110 doesn't cut it. Call it a 'German P-51' if you like, though it doesn't need such extreme range as London->Berlin and back. But say Northern France to Southern England, fight for a good while to protect the bombers, then get back with fuel to spare. Probably not an easy ask for the late 1930'ies to design such a plane, though.

Minimum effort should've been an early drop-tank installation for the Bf 109.
The He 100 with two drop tanks? The DB 601-powered short-winged Fw 190?
Something of size and shape of the Spitfire/Mustang/P-40?

 

[z42]

There are several points to consider. The 1/2 tracks were a huge advantage in poor weather/bad roads.
On good or even medium roads the advantage disappeared. Most of the Maultier types averaged a max speed of around 40kph. average speed is going to be lower.
Most of the German trucks could max out at 70-85kph depending on model (some were slower) but unless on really good roads they are going to be going slower, just not as slow as the Maultier. The Maultier is going to get bad mileage. Turning the tracks takes more power than making the wheels roll. Some specs say about 1/2- 2/3 the range of the wheeled truck using the same fuel.
Maultier was simple to build. Same driveline and steering of the parent truck.
When you needed a Maultier you needed a Maultier. When you didn't it sucked up fuel, was slow and carried less cargo.
The fancier German 1/2 tracks were rather expensive. They had a much more sophisticated suspension and a much more sophisticated (complex) steering system. For shallow turns the steering wheel just turned the front wheels. For sharp turns the the steering wheel activated track brakes like a tank slowing/stopping the inside track.
The Germans never (rarely?) put a powered front axle on their 1/2 tracks. This hurt some of the mobility/steering. The front wheels tended to plow in bad going.
The fuel mileage of the military 1/2 tracks was not good. The unarmored 3 tonner was supposed to get 240 km using 110 liters of fuel. A 3 ton Opal was supposed to get 320km on 82 liters. Again, when you need the unarmored 3 tonner 1/2 track you need it (towing a 10.5cm howitzer cross country) but for hauling ammo and food on a packed dirt road?
BTW the Ost-schlepper maxed out at just over 17kph. A very interesting and useful vehicle but as a general supply vehicle (large loads over long distance) it sucked.

Logistics is a very, very hard game.

Half-tracks were sort of an ad-hoc solution to the question of how to improve cross-country mobility of a truck chassis, without having to involve the full complexity of a tank-style gearbox for steering. But once you decide you need the ability to steer with the tracks, there's little advantage to keeping those front wheels and you're better of with a fully tracked vehicle. Half-tracks disappeared for good reasons pretty soon after WWII. Note, not saying they were a stupid idea, in a way they were actually a clever solution for how to quickly get large numbers of vehicles capable of difficult terrain out in the field. But they were an approach with many compromises.

And if you can somehow make do with wheels alone, they offer big advantages in speed and fuel consumption, as mentioned, but also maintenance requirement.

 

[Shortround6]

Intermediate cartridge ASAP.

This allows for more ammo from the same amount of resources. Labor and machine time goes up.
Reduces total need for transport for the same number of rounds.
If you use MP 44s (or ancestor) instead of K 98s you need more ammo.
You still need 7.9 X 57 for the machine guns.

Using a 6.5mm cartridge instead of the short 7.9mm means a bit more new tooling and it may mean a substantial shift in production to new guns and a more complicated logistics while the change over occurs.

An actually fast bomber. Something size of Me 110 (the Ju 88 is too big); the earlier the Do 17 is phased out, the better.

Me 110 needs a fatter fuselage. This is actually quite simple. Just stick the longer fuselage on the Me 210 and toss the remote MG 131 rear guns in the bin.
A lot depends on what you want the bomb load to actually be and what range you actually want.
The Ju 88 actually sucked at carrying large (250kg and up) bombs. It also sucked at carrying much inside and going very far.
Trying for fast bomber and carrying more than two bombs externally is not a good plan. It even a good plan for carrying a pair of bombs externally.

Spitfire-sized, and as sleek fighter-bomber/ LR fighter/recon.

Yes, Germans were behind on aerodynamics. They need a fast fighter with larger than a 200sqft wing with sufficient fuel. Doesn't have to be P-51 fuel but on the other had, 500 liters and a radial engine does not buy much for range.

Axe the Hs 129.

Just accept it for what it is/was.
You want 900-1100hp engines and the fuel to go with them?
You have a small/medium bomber. Put a pointy nose on the Do-17 and some armor plate and have at it.

2-seat versions of 1-engined fighters for training ASAP.

And/or better single seat trainers

Argus 240hp engine. 11.6 sq m of wing. Wood construction (at least the wing/tail), High wing loading will somewhat mimic the landing of a 109.
Max speed of 335kph is low. Version with a 465hp Argus?

 

[Shortround6]

BoB showed that Germany would have needed a fighter capable of long range escort missions. No, something clunky enough that it gets easily shot down in droves by enemy day fighters like the Bf 110 doesn't cut it.

The 110 actually did pretty well against the Hurricane. Did OK against the French fighters.
Now it did have a few problem, the 3 seat cockpit design added some bulk/drag. Came in handy for some later rolls.
We also run into a technology hiccup. German radios in single seat fighters had crap for range. The 110 used the same radio as the He 111, great range but large, bulky and needed a radio operator to manage the antenna and code key for transmitting.
Radios got a lot better real quick but when you are placing contracts and planning factories in 1938-39 what are you planning for?

Possibility to have more internal fuel, and it might've been had in numbers for the whole 1940. Indeed, the better landing gear.
A few advantages in streamlining, like the smaller and probably a more advanced wing, non-protruding ram air intake, wheel well covers as-is - these can add up neatly.

The He 100 got some of it's performance from a small wing and a small fuselage. One reason the MGs were in the wing root, not enough room in the fuselage.
Expecting to hold both more fuel and more armament in a smaller aircraft might be asking too much.

 

[z42]

- Intermediate cartridge ASAP.

This allows for more ammo from the same amount of resources. Labor and machine time goes up.
Reduces total need for transport for the same number of rounds.
If you use MP 44s (or ancestor) instead of K 98s you need more ammo.
You still need 7.9 X 57 for the machine guns.

Using a 6.5mm cartridge instead of the short 7.9mm means a bit more new tooling and it may mean a substantial shift in production to new guns and a more complicated logistics while the change over occurs.

If you're going to go for an intermediate cartridge Germany should do it before choosing the K98K and manufacturing millions of them. Which means 1935-ish. Can we invent and get the Stg 44 into service almost a decade earlier than historical? Sounds like quite a lot?

Or then they end up like Japan which was in the middle of an infantry rifle caliber transition during the war.

Alternatively, keep the K98K but deploy MP 40 more aggressively? If a rifle squad has, say, half the guys with rifles and half with SMG's, between the rifles and the MG's that's still plenty of long range firepower.

Let's also not forget that something like 70% of infantry casualties were due to artillery. Add in other unpleasant ways of dying like direct fire cannons (tanks, infantry guns, whatnot), hand grenades, machine guns etc. etc., and the remaining % due to small calibre rounds fired from individual weapons might not be particularly large. Ergo, it might not be particularly decisive whether the individual infantryman is equipped with an early assault rifle, or a combination of bolt action rifles and SMG's?

 

[tomo pauk]

This allows for more ammo from the same amount of resources. Labor and machine time goes up.
Reduces total need for transport for the same number of rounds.
If you use MP 44s (or ancestor) instead of K 98s you need more ammo.
You still need 7.9 X 57 for the machine guns.

Using a 6.5mm cartridge instead of the short 7.9mm means a bit more new tooling and it may mean a substantial shift in production to new guns and a more complicated logistics while the change over occurs.

Germans were faced with the same dilemma back in ww2, their decision was still to go with the 8mm Kurz. Going very early with that decision has the merit, IMO.
LMGs can work well with intermediate cartridges, see the different Soviet weapons between 1950 and 1980.

I'm not sold on 6.5mm new-construction weapons for the German needs.

Yes, Germans were behind on aerodynamics. They need a fast fighter with larger than a 200sqft wing with sufficient fuel. Doesn't have to be P-51 fuel but on the other had, 500 liters and a radial engine does not buy much for range.

Oh, no radial for the LR job. Keep the DB 601/605, and 600L of fuel + drop tank possibility.

Just accept it for what it is/was.
You want 900-1100hp engines and the fuel to go with them?
You have a small/medium bomber. Put a pointy nose on the Do-17 and some armor plate and have at it.

I'm trying to axe it for what it was between 1939 and 1942.
The Do 17 trying to act as a tree-top attacker is the AA gunner's dream come true. I'd rather have something small and fast instead. Preferably, 1-engined.

And/or better single seat trainers
Argus 240hp engine. 11.6 sq m of wing. Wood construction (at least the wing/tail), High wing loading will somewhat mimic the landing of a 109. Max speed of 335kph is low. Version with a 465hp Argus?

At any rate, German training program went south very early, so any improvement is a boon to the LW.

The He 100 got some of it's performance from a small wing and a small fuselage. One reason the MGs were in the wing root, not enough room in the fuselage.
Expecting to hold both more fuel and more armament in a smaller aircraft might be asking too much.

Fuel tanks are in the wings on the He 100, while a good deal of the fuselage behind the pilot (where the Bf 109 will have a fuel tanks) was occupied with the oil tank, alcohol tank, respective pumps and the heat exchanger between the two. Normal oil cooler removes the need for all these ancillary systems, so an additional fuel tank can fit.
Not having the condensers and coolant tanks in the wing frees a lot of space there.
Anyhow, it will not be the "early Tempest", but it might be a longer-ranged Yak-3 above 5 km.

 

[Elan Vital]

Good idea.



A BMW 132 with a 2-speed S/C is already an improvement vs. the 'normal' 132. To their detriment, neither the BMW nor Bramo were good in making modern superchargers until well into ww2; retrofit of a better S/C on either the 132 or 323 would've gave them perhaps another 100 HP between S/L and, say, 4km?
Germans made a ... curious choice when they decided what to get from the G&R. Seems like the most popular engine was the least capable one, the 14M, that meant one needed two of such in order to make an aircraft acceptable. Focusing on the 14N instead would've netted them more, IMO. Let alone on the 14R. It is not a long shot for them to be getting the 14N already in 1940 (= engines already made + what can be produced), and make a switch to the 14R by the winter of 1941/42. If the Hs 129 is cancelled (preferably even before it took 1st flight), the captured 14M can be used on the transports.
This is perhaps where the 'how they could've used better the war booty' part starts.

When France drew up a revized aircraft production plan on May 28 1940, they decided to produce more 14Ns instead of 14Ms since production of Potez 63 with this engine was reduced with the loss of the Méaulte plant. Apparently, GR could make either engine. I guess the N would make more sense for non-combat aircrafts that don't need as much effort as fighters for the integration of a new engine. The 14R was one of the items under development by Vichy and/or asked by Germany as part of the 1941 joint air program they agreed upon, and since this one had a competitive supercharger and performance, it might now be suitable for combat aircrafts. It did require 93/100 octane fuel though, but same deal as BMW 801.

France/Vichy was quite an oddball compared to what Germany did the Czechoslovakian industry. It took until 1941 to get a joint production program for the Axis (and limited Vichy defenses) even though the collaborationist group had prevailed in the Vichy regime since Fall 1940 if not earlier, and Vichy was not allowed to do certain improvements (the HS-12Z was denied as well as drag reduction upgrades for D-520 at one point). I understand that French tooling and ressources were partially looted and that May/June 1940 mobilized production could not be restored in full, but I suspect a better compromise could have been reached, considering that post-Fall France still had at least the 3rd biggest military-industrial complex after Italy under Axis control.
Considering the Germans and Axis constantly lacked certain items and that setting up new capacity in the Reich would take time anyway, using the near-immediate capacity of certain French factories would help. Certain French designs were superior or at least a good equivalent to what non-German Axis had for most of the war when Germany couldn't prop up her allies so much. Oh well, I still got to grab the archives on Vichy weapon studies (there is one!) and the joint program for air production.

Admittedly, making the best of the remaining French industry might require a different territorial layout with possibly a larger Vichy France (up to the Parisian industrial region), which would however be a very good concession to obtain that reinforced industrial cooperation.

Calum Douglas pointed out how problematic the German effort on aircrafts and engines was. There were quite plainly too many projects to handle. Cross polination between DB and Jumo for the V12s would already have been useful to help solve the issues with both engines (mediocre SC and 2 valves on Jumo, less efficient construction and worse lubrication on DB). Maybe ditch all the non-conventional engines (bundled engines, Jumo 222, DB 609 V16) and instead focus on the existing types with an effort towards better S/Cs since that's how the promising late projects were mainly improved. In the case of the BMW 801, maybe the two-speed cleaned up S/C of the GR 14 R 04/05 could help.

 

[Shortround6]

Germans were faced with the same dilemma back in ww2, their decision was still to go with the 8mm Kurz. Going very early with that decision has the merit, IMO.
LMGs can work well with intermediate cartridges, see the different Soviet weapons between 1950 and 1980.

The trouble is you still need the full power rounds for machine guns. Of course this somewhat depends on doctrine and a lot of times doctrine has been faulty.

A lot of doctrine depends on the distances a country expects it's units to fight at. And this gets a little complicated.
What distance is the squad expected to fight at?
Except that the squad rarely fights alone, it is part of a platoon. any increase in distance for the platoon?
And the Platoon is part of a company and here is where many armies start to split off, especially at different times.
British used the Bren gun for everything, it was their GPMG except they didn't call it that. There were supposed to be tripods for long distance fire, prepared positions held at company level for use by the squad/platoon guns. That was doctrine. Practice was rather different. Germans were much the same, the actual fire power of the company was the light machine guns of the squads with support by sometimes a heavy weapons platoon and or tripods held in company store. Germans at times adopted short 81mm mortars as company weapons.
US had their rifles and BARs and two 1919s at company level and 2-3 60mm mortars.

In the 1950s-80s the Soviets gave at least two belt feed RP-46 machine guns to each company as support (long distance) weapons.
The US and NATO were all over the 5.56mm machine guns and assaults rifles in the 60s through 80s/90s. Until they got into actual combat at less than urban/jungle distances.

So do you introduce the intermediate cartridge for some cost savings but have to keep the older/larger cartridge in stock/manufacture anyway?

I'm not sold on 6.5mm new-construction weapons for the German needs.

I love the 6.5 for target use. As a military MG round I have reservations. It is not a good size for 'payloads'. It might be OK for tracer but holding around 1/2 to 2/3rds (at best) of incendiary material does limit it. How effective an AP round it would be is also subject to question. Yes you are trying to make a smaller hole but you have less mass to do it with.
You can't shrink the projectile in proportion. If you want to come close to the full bore AP performance you need a steel core just as long as the full bore (7.5-8mm) projectile but skinner. Thing here is that you also can't scale down the bullet jacket thickness at the same rate you scale down the overall diameter. You wind up with a slightly skinner penetrator than you might expect.

Of course if you are going to go to the two cartridge solution (short 7.5-8mm + long 7.5-8mm cartridges) then adapting a 6.5 instead of the short 7.5-8mm round is a lot easier to get behind. The short 7.5-8mm rounds have lousy capacity for tracer, incendiary or AP performance.

 

[marathag]

So my suggestion is that a new transport aircraft is developed, widebody, high wing, with two or three engines, that will be no worse that the Bristol Bombay or the Italian 3-motors, respectively. Main materials being steel, wood and canvas.
On the back burner, have the Ju 52 tested with just two and one engine, and with greater incluson of not-light alloy materials; cunning plan is that the Ju 52/1m is the monoplane equivalent of the An-2 Colt (or, a more powerful version of this).

Or the Boring 'Buy American' via an Italian-American, Giuseppe Bellanca.

Steel tubes and some wood construction Sesquiplane

The single engine and wing construction limited it's use in the USA with the new FAA rules in place. So Mr Bellanca looked for buyers, Earlier Aircruisers with a single engine was popular in Canada and the Columbian Armed forces were able to trade some coffee for some of these twin engine bomber versions

Faster, longer ranged with twice the bombload over the Ju-52, with two 650hp motors

From wiki

Bellanca 77-140 Bomber
General characteristics

• Crew: two, pilot and gunner [as Transport, 15 passengers]
• Length: 40 ft 0 in (12.20 m)
• Wingspan: 77 ft 0 in (23.48 m)
• Height: 14 ft 0 in (4.26 m)
• Gross weight: 12,250 lb (5,560 kg)
• Powerplant: 2 × Wright R-1820 , 650 hp (485 kW) each

Performance

• Maximum speed: 180 mph (290 km/h, 160 kn)
• Range: 700 mi (1,120 km, 610 nmi)
• Service ceiling: 20,000 ft (6,100 m)

Armament

• 2 × .30 caliber machine guns
• 2,200 lb (1,000 kg) of bombs

Ju-52
General characteristics

• Crew: Two
• Capacity: 17 passengers
• Length: 19 m (62 ft)
• Wingspan: 29 m (96 ft)
• Height: 5.5 m (18.2 ft)
• Wing area: 110.50 m2​ (1,189.4 sq ft)
• Empty weight: 5,720 kg (12,610 lb)
• Gross weight: 9,500 kg (20,944 lb)
• Max takeoff weight: 10,500 kg (23,146 lb)
• Powerplant: 3 × BMW 132A-3 9-cylinder air-cooled radial piston engines, 510 kW (680 hp) each for take-off (510 kW (690 PS)[90]​)
• Propellers: 2-bladed fixed-pitch propeller

Performance

• Maximum speed: 265.5 km/h (165.0 mph, 143.4 kn) at sea level

276.8 km/h (172.0 mph; 149.5 kn) at 900 m (3,000 ft)

• Cruise speed: 246 km/h (153 mph, 133 kn) maximum continuous at 910 m (3,000 ft)

209 km/h (130 mph; 113 kn) economical cruise

• Range: 1,000 km (620 mi, 540 nmi)
• Service ceiling: 5,900 m (19,360 ft)
• Rate of climb: 3.9 m/s (770 ft/min)
• Time to altitude: 3,000 m (9,800 ft) in 17 minutes 30 seconds
• Wing loading: 83.35 kg/m2​ (17.07 lb/sq ft)
• Power/mass: 7.95 kg/kW

Armament

• Guns: * 1 × 7.92 mm (0.312 in) MG 15 machine gun or 13 mm (0.51 in) MG 131 machine gun in a dorsal position
• 1 × 7.92 mm (0.312 in) MG 15 machine gun in a semi-retractable dustbin turret
• Bombs: up to 500 kg (1,100 lb) of bombs

 

[tomo pauk]

Or the Boring 'Buy American' via an Italian-American, Giuseppe Bellanca.
Steel tubes and some wood construction Sesquiplane
The single engine and wing construction limited it's use in the USA with the new FAA rules in place. So Mr Bellanca looked for buyers, Earlier Aircruisers with a single engine was popular in Canada and the Columbian Armed forces were able to trade some coffee for some of these twin engine bomber versions
Faster, longer ranged with twice the bombload over the Ju-52, with two 650hp motors

One-engined Ju 52 was carrying 1000 kg over 1000 km, while being powered by unsupercharged engines. Stick an 850-900 HP supercharged radial on that A/C and there it is - a no-nonsense transport that can be cheaply purchased, that sips the fuel and that will require far less of maintenance than the 3-engined siblings. Invest some thought in replacing the light alloy parts - where possible - with steel/wood/canvas while you're at it.

 

[tomo pauk]

The trouble is you still need the full power rounds for machine guns. Of course this somewhat depends on doctrine and a lot of times doctrine has been faulty.

So do you introduce the intermediate cartridge for some cost savings but have to keep the older/larger cartridge in stock/manufacture anyway?

The full-power cartridges are there to stay. After all, even when the intermediate cartridges took off in the 1950s-60s, nobody removed the full-power cartridges and the respective MGs from the inventory. The vehicles will still be using these, after all.

Of course if you are going to go to the two cartridge solution (short 7.5-8mm + long 7.5-8mm cartridges) then adapting a 6.5 instead of the short 7.5-8mm round is a lot easier to get behind. The short 7.5-8mm rounds have lousy capacity for tracer, incendiary or AP performance.

The 6.5mm weapons will require all the new barrel-boring machines, unless there is a good foresight around to involve the captured machines (from Austria, Netherlands Belgium at 1st?) in the considertaion? Not to say that was impossible to do in Germany if so decided early on, but it is a greater investment than to go with an 8mm short cartridge.
But anyway, either of the two are a better thing to do than to insist on the full-power cartridge until mid-ww2.

 

[tomo pauk]

France/Vichy was quite an oddball compared to what Germany did the Czechoslovakian industry. It took until 1941 to get a joint production program for the Axis (and limited Vichy defenses) even though the collaborationist group had prevailed in the Vichy regime since Fall 1940 if not earlier, and Vichy was not allowed to do certain improvements (the HS-12Z was denied as well as drag reduction upgrades for D-520 at one point). I understand that French tooling and ressources were partially looted and that May/June 1940 mobilized production could not be restored in full, but I suspect a better compromise could have been reached, considering that post-Fall France still had at least the 3rd biggest military-industrial complex after Italy under Axis control.

Getting a good deal of HS production resources to be devoted as a support for the Italian production of V12 engines would've improved the Italian engine situation. Historically, even with that production underway at AR and Fiat, Italins were still getting their V12s in meager quantities, meaning that Germany needed to step up, both in engines and whole aircraft, to improve the Italian air force capabilities.

Calum Douglas pointed out how problematic the German effort on aircrafts and engines was. There were quite plainly too many projects to handle. Cross polination between DB and Jumo for the V12s would already have been useful to help solve the issues with both engines (mediocre SC and 2 valves on Jumo, less efficient construction and worse lubrication on DB). Maybe ditch all the non-conventional engines (bundled engines, Jumo 222, DB 609 V16) and instead focus on the existing types with an effort towards better S/Cs since that's how the promising late projects were mainly improved. In the case of the BMW 801, maybe the two-speed cleaned up S/C of the GR 14 R 04/05 could help.

Indeed, forget the bundled engines, the 222, the BMW engines beyond the 801, and the DB engines with more than 12 cylinders. The BMW 801 with the S/c and intake of the 14R 04/05 would've been much better above 4 km, let alone above 6 km.
The DB 603 was pretty much a low-hanging fruit, not pausing it's development would've been a right call for the LW/RLM. Yes, the DB engines will need the much better lubrication to be in play, not to wait until late 1943 to implement that.

The S/C on the Jumo 211 was pretty good from the F version and later, the valve gear was with 3 valves, not 2. Both the 211 and the 601/605 would've benefited with a big S/C installed early on, let alone with a 2-stage S/C, while the already decent low-/mid-altitude performance could've been improved by installation of the swirl throttle.

 

[Shortround6]

Invest some thought in replacing the light alloy parts - where possible - with steel/wood/canvas while you're at it.

Then why bother?
Just design (or buy) a non-light alloy aircraft to begin with.
Junkers did a heck of a job designing the manufacturing set up for the Ju 52, but it a complicated aircraft to build.

It also was an aerodynamic as a brick wall.

It is very hard to figure out how to have more sq meters of surface area for the air to flow over while coving so few sq meters of wing or fuselage area. And the air did not follow the groves. It often wanted to slide up or down or left and right.

The Sooner the Germans consign the Ju 52 (however good it may have been in 1930-32) to museums, the better off they are going to be.

 

[Shortround6]

The 6.5mm weapons will require all the new barrel-boring machines,

Not really. The machines will be the same, what changes are the drill bits and reamers and since those wear out/break anyway and are replaced on fairly regular basis it is not that big a deal. The actual boring machines are going to need more than one drill anyway and a finishing reamer. They don't really care what size drill bit you put in the machine (lathe?)
Now for the rifling you do have to change a bit more stuff. I believe in WW II and before the standard was cut rifling. So you need cutters or cutter heads to make the new grooves (one stroke at a time) and you need a new frame/guide to turn the cutter at the right twist.

Now you have several ways to go about this. Make 8mm barrels for a few weeks and then make 6.5 barrels for a few weeks as demand dictates or devote some machines to 8 mm production all the time and some to 6.5mm production.
Now the dept or outside supplier of the drill bits, reamers and cutters may like making the same things 100% of the time but it is not really that big a deal.

 

[Shortround6]

Getting a good deal of HS production resources to be devoted as a support for the Italian production of V12 engines would've improved the Italian engine situation.

It would help but not as much as you think, unless you want the Italians to build/use HS 12Y engines.
Birkigt was a genius in many ways and he designed special machinery and fixtures to make his engines. But changing them over to make other things was hard.
The HS engines used all their valves in a row. You could start machining the valve stem area and valve seat area on one end of the cylinder head and just keep advancing down the head. But it was even both more complicated and simpler than that. I don't know if he had machines that worked on more than one valve at a time or if he had machines that would automatically index the head to the next point. The outcome was that Hispano engines often used the same bore spacing and valve spacing, sometimes even from V-8 engines to V-12s. Breaking away from the classic Hispano engines, even to change to 3 valves instead of 2 was a major undertaking, retooling.
Getting lathes that you could make DB crankshafts on would certainly help. But you need to come up with all the tooling and fixtures that go between the basic lathe and the parts being worked on. Tooling can include things like snap gauges.

Something where the production machinist can just put go-no go gauges on the part/s, or inspectors.
The next question is how much was HS making from start to finish or what were they using for suppliers of forgings and castings?
Getting the machine tools and having the forge/foundry hundreds of km away may not help a lot. Italian industry may have been running near capacity for a number of things.