Japanese logistics, purchase programs and war booty, reality and alternatives 1936-44

[Shortround6]

If Wiki is right and the main change of the Mod 5 is the stronger buffer springs, I'd imagine it would be relatively easy to introduce that earlier in the timeline, no? The fire rate doesn't need to be stratospheric, but 480~500 rpm is unnaceptable for a 20 mm.

The 20mm Oerlikon traces back to the Becker gun of 1915 (patent was from 1913).
Order for 120 guns was placed in June 1916. By the end of the war The Allies found 362 guns, actual production is unknown. 1921 saw the transfer of the rights to the SEMAG of Switzerland.
Ehrhardt was working on a competing gun in WW I that was short recoil, scaled up from the Dreyse machine gun of 1912. Perhaps 51 guns were built(?) all but a few disappeared at the end of the war. Rights were transferred to Solothurn.
Granted in 1920s the world was not rushing to by new weapons but they had just under 20 years to work on them before WW II broke out. You also have a number of arms designers (mostly in Europe) trying to design alternatives that were lighter, more powerful, faster firing and any other improvement you can think of. The The Oerlikon F started at about 300rpm, slightly up from the 250-300rpm of the WW I guns. They got around 400rpm out of it by the early 30s. Different accounts use different numbers (different tests or advertisements?) By WW II the shorter guns were getting into the low 500rpm range.
The long cartridge FFS never really got over 500rpm during WW II and many of 1930s versions were barely over 400rpm.
There were a lot of people making Oerlikon guns of different sizes in different countries for a number of years from the mid 30s to end of WW II. And all somebody had to do was change the spring?
Wiki is correct, basically, that is the major change. But getting the gun to function correctly using all ammo types and in all conditions is a lot harder. See the trouble the Germans had with the MG FF and MG FFM. You can load the older FF ammo into the magazines of the FFM and the gun will fire, at least for a short time.
I will note that nobody says you can take an FF and turn it into an FFM simply by changing the spring.
I will also note that the 20mm FFS series of guns (ground AA) required lubricated ammo (greased/waxed) to function reliably in different weather conditions. And a cold gun is going operated differently than a hot gun.
The API blowback system of the Oerlikon guns requires a careful balance of reciprocating weight, initial spring pressure and spring pressure/tension throughout the bolt travel balanced against the pressure in the chamber/barrel. It is getting the balance correct that requires a lot of time/testing.

 

[Shortround6]

See it from the Japanese PoV. A pair of Ho-3 cannons (plus perhaps a pair of LMGs for the feel-good feeling) is far cry vs. even the heaviest firepower the Ki-43 had. Even the Ki-43 and Ki-61 were initially with just 2 LMGs and 2 HMGs.
I have nothing against the better and more refined weapon, just that this is available historically, and can do the job until these better weapons arrive.

The Japanese needed a heavier, more powerful fighter than the Ki-43. A big wing Ki-44 (think primitive Ki-84) might have been able to carry a pair of Ho-3 cannon. Now the question is is if a single slow firing Ho-3 in each wing was better than a pair of 12.7 Ho-103s in each wing or a pair of Navy type 99-Is ?

Japanese-produced guns were generally pretty light, from 30 to 50 kg.

That is true but the lighter guns tend to use smaller, lower powered ammo. Gun designers were not stupid. They often worked to different requirements. Gun designers did not tell the Generals and Admirals what they needed. They might suggest what they thought they could do but the 'brass hats' wrote the requirements and issued the contracts.
Some real big unknowns were both the required reliability (jams/malfunctions per 1000 rounds?) and durability (life of the gun). Soviets traded durability for weight.
Japanese emphasized light weight armament to get high performance aircraft.
US saddled a lot of their early war aircraft with way too much weight in guns and ammo.

 

[tomo pauk]

The Japanese needed a heavier, more powerful fighter than the Ki-43. A big wing Ki-44 (think primitive Ki-84) might have been able to carry a pair of Ho-3 cannon. Now the question is is if a single slow firing Ho-3 in each wing was better than a pair of 12.7 Ho-103s in each wing or a pair of Navy type 99-Is ?

There is no such thing as an ideal historical ww2 gun?
A Ki-44 might've worked as-is with a pair of either Ho-3s or the Navy's cannons. Sprinkle with some HMGs or LMGs to taste.
The FFL might've been the best fit - it was not some awesome 20mm weapon, but it has no actual shortcomings (be that in weight, size, RoF or MV), bar the late start as far as the Japanese go. It's slender ammo was also a bonus, more could be packed in the volume than the bottlenecked 20mm rounds.

That is true but the lighter guns tend to use smaller, lower powered ammo. Gun designers were not stupid. They often worked to different requirements. Gun designers did not tell the Generals and Admirals what they needed. They might suggest what they thought they could do but the 'brass hats' wrote the requirements and issued the contracts.
Some real big unknowns were both the required reliability (jams/malfunctions per 1000 rounds?) and durability (life of the gun). Soviets traded durability for weight.
Japanese emphasized light weight armament to get high performance aircraft.
US saddled a lot of their early war aircraft with way too much weight in guns and ammo.

Japanese 20mm stuff was pretty reliable, or, at least there are no Allied reports on these being problematic. Perhaps the people designing and making guns were simply good in what they were doing?
The HMGs were decent by mid-war, but going with HE stuff on the HMGs was both not worth it (bang for buck) and IIRC was cause of premature detonations on the Ki-43.

 

[Shortround6]

There is no such thing as an ideal historical ww2 gun?
A Ki-44 might've worked as-is with a pair of either Ho-3s or the Navy's cannons. Sprinkle with some HMGs or LMGs to taste.
The FFL might've been the best fit - it was not some awesome 20mm weapon, but it has no actual shortcomings (be that in weight, size, RoF or MV), bar the late start as far as the Japanese go. It's slender ammo was also a bonus, more could be packed in the volume than the bottlenecked 20mm rounds.

You are correct, there was no 'ideal' 20mm historic WW 2 gun.
The Hispano was good, but it took a while and it was heavy, there was no powerful but light gun. Sort of pick one or the other
The FFL/type 99-2 might have been good, not the best but it was closer to the Hispano while weighing less.
The Ho-3 ammo was fat, About 7mm or about 33% fatter than the 20 x 72RB and 20 x 99RB of the Japanese Oerlikons. Not so important with the 50-60 round magazines/drums but when you are heading towards 100 rounds and the fatter shells will only allow around 75 instead if 100?

Japanese 20mm stuff was pretty reliable, or, at least there are no Allied reports on these being problematic. Perhaps the people designing and making guns were simply good in what they were doing?
The HMGs were decent by mid-war, but going with HE stuff on the HMGs was both not worth it (bang for buck) and IIRC was cause of premature detonations on the Ki-43.

Most WW II guns were not built on the cheap model, except some Soviet guns and a few German? That came later.
Just pointing out the trying for a light weight gun can have consequences. That is lighter than average for the performance. You can have a light gun that is reliable and long lasting if you give up some performance factors. Japanese had been fighting in China for a number of years, slowly expanding southward. They had also been operating in Manchuria for a while and were familiar with supply/logistics.
Japan was also a small country Industry wise. There was not the car industry or even an industry that made large numbers of washing machines or refrigerators. Car production was more on the order of 0.1% rather than even 1% of US production. Or even less. Under 12,000 trucks buses and cars built in 1939? A lot of their steel production went to the Military even in the 1930s. There wasn't a lot of industry to convert over.
The Japanese did a lot of good work but they also didn't have the engineers and technical people. The US had enough people and enough resources to train people during the war, It was not unlimited but the US Industry also planed for schools or training areas to train people for weeks or months before they stuck them into a number of jobs in the factories. Not training on the job as an apprentice. The American way got more people semi-trained faster. It might not have given more well trained (higher skill levels) after one or more years.

The whole 12.7mm explosive bullet idea might have been a mistake, for any nation. The Japanese were trying to do away with the expensive fuse.
A 12.7mm round held around 1/5 to 1/10 of the HE of a 20mm shell. If you used a fuse it did not cost only 1/5 to 1/10 as much because it was smaller.
But 12.7mm AP or incendiary (no fuse) may show a large advantage over 7.7mm bullets.

 

[tomo pauk]

The Ho-3 ammo was fat, About 7mm or about 33% fatter than the 20 x 72RB and 20 x 99RB of the Japanese Oerlikons. Not so important with the 50-60 round magazines/drums but when you are heading towards 100 rounds and the fatter shells will only allow around 75 instead if 100?

This is the reason why I was suggesting that the 20mm ammo should've been necked-up to 23mm, as well at the "Ho-3/23" is made - since we're already paying the price in bulk and weight, have it at least provide a considerably greater punch than the 20mm stuff. A 180-200 g shell vs. ~130g?

The whole 12.7mm explosive bullet idea might have been a mistake, for any nation. The Japanese were trying to do away with the expensive fuse.
A 12.7mm round held around 1/5 to 1/10 of the HE of a 20mm shell. If you used a fuse it did not cost only 1/5 to 1/10 as much because it was smaller.
But 12.7mm AP or incendiary (no fuse) may show a large advantage over 7.7mm bullets.

Yes, the AP(I) is the way for any HMG, IMO.

 

[z42]

This is the reason why I was suggesting that the 20mm ammo should've been necked-up to 23mm, as well at the "Ho-3/23" is made - since we're already paying the price in bulk and weight, have it at least provide a considerably greater punch than the 20mm stuff. A 180-200 g shell vs. ~130g?

For aircraft autocannons there might be a case to be made for a relatively short and stubby shell giving decent enough MV with a more or less straight walled cartridge? Not as efficient ballistically as a thinner and longer shell of the same weight, but at realistic shooting ranges might not matter.

Yes, the AP(I) is the way for any HMG, IMO.

Agreed.

 

[marathag]

Kayaba Ka-1 Autogyro

based off US design, was a good utility aircraft used by the IJA.

Including ASW, from the Army Escort Carriers, since the IJN was so bad at ASW.

Make more, and for both service Branches. Then work on improved models with more payload.

 

[tomo pauk]

For aircraft autocannons there might be a case to be made for a relatively short and stubby shell giving decent enough MV with a more or less straight walled cartridge? Not as efficient ballistically as a thinner and longer shell of the same weight, but at realistic shooting ranges might not matter.

From what I can gather, most of the times people went with a (very) powerful cartridge, the resulting gun for that cartridge was with major shortcomings as a gun for air fighting. Either the gun was too big to fit neatly, or it was very heavy, or it recoiled badly, or the RoF was slow, or the ammo count was low, or the shell was too light, or a combination of the above. Now, such guns would've be doing great as AA pieces, or even as flying AT artillery, but installing them on a modestly-sized fighter was a tough job.

So yes indeed - aim for a more modest MV (but not too modest), that keeps the gun recoil, size & weight manageable, RoF is good, shell weight & count is good; basically, one has a good/great gun to fight aerial targets on the normally short distances in the ww2.

 

[GrauGeist]

I believe Snowygrouch referenced this as well in one of his posts but I could not find it using Snowygrouch, as the search term is no longer usable due to his leaving the

Callum's user name is hard to search for, but I was able to find it via his Secret Horsepower Race book thread:

"The Secret Horsepower Race" - Available to pre-order