Japanese change from 6.5mm to 7.7mm

Joel

Joel

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Has anyone ever seen any source material on why the Japanese changed from 6.5mm to 7.7mm?

I mean, I know they wanted a larger caliber. Obviously. But ever come across anyting explaining just why they felt 6.5x50 was inadequate?

(Same for Italy, actually)
 
Source no, but supposedly the technology of the time couldn't make an effective tracer, an idea supposedly first proposed by Robertson (from Ontario), the inventor of the Robertson Screw.
 
MiG25 said:
Source no, but supposedly the technology of the time couldn't make an effective tracer, an idea supposedly first proposed by Robertson (from Ontario), the inventor of the Robertson Screw.
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Oh thanks MiG! That's interesting!

Makes sense too, in the way that I can't imagine how they were deficient in the battlefield otherwise. Hard to imagine them not getting the job done.
 
That the early Type 99 Arisaka had anti-aircraft sights may be related to the tracer idea.

Of course by the time WWII rolled around it was pretty quaint to think of shooting down an airplane with a rifle.
 
Snider shooter said:
Everything I have read about the change over related to this. Japan was at war with China for years and found the 6.5 lacked in performance.
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Does the 7,7 actually outperform the 6.5 at say 1500-2000 yards in a machine gun?

Japan brought out a 7.7.
Sweden the 8x63
Italy the 8x59 Breda

All for machine gun use with tracers, incendiaries, etc.

I'm not up on military loads, but did these countries even issue these type of loads at the time for the 6.5's?

I suspect Italy brought out the 7.35 with the plan to rebore the millions of 6.5 rifles they had to freshen the bores. Like Portugal did going to the 8x57. Remember Italy was (and is) a poor Country.
 
Japanese aircraft were fitted with Type 92 and Type 97 machine guns, which were Lewis and Vickers gun copies respectively. These were chambered in .303 British, which is 7.7 mm but was NOT 7.7 Japanese rimless or 7.7 Japanese Semi Rimmed, it is separate round (7.7x56R).
As mentioned above, long range performance from machine guns and effect on armored targets were not ideal with 6.5x50. The .303 British copy and machine guns were in use for aircraft by 1932, but all the designs of 6.5 machine guns weren't easily converted to .303 with its large rim so a rimless round was needed to work in these designs. Example, Type 96 LMG in 6.5x50SR being replaced by Type 99 LMG in 7.7x58 mm with minimal redesign.
Their experience already manufacturing .312 barrels and projectiles is why the diameter is shared between .303 British and 7.7 Japanese.

Naturally the result was logistical anarchy. I was on Guadalcanal in October and saw Type 92, 96, 97 and 99 machine guns, Type 38 and 99 Arisakas, plus a few Dutch Madsens meaning they had 6.5 Japanese, 7.7 Japanese, .303 British and 6.5x53R all in use at the same tme...

I know that is a little less clear on the exact details behind why 6.5 was seen as inadequate, but helpful on why they settled on 7.7 specifically.
 
6.5x50sr was also a semi-rimmed round which makes designing machine guns more difficult. Basically the worst of the choice between rimmed and rimless as it carries all the disadvantages yet no benefits.

I suspect the main reason though was a more combat effective round. Japan and Italy both at this point had substantial experience with the 6.5 and basically every nation with a ton of combat experience with it went to something bigger. My best guess is the biggest advantage 6.5 had (flat trajectory) really went out the window with the development of spitzer bullets in the early 1900s. Basically all the 6.5s were adopted in the 1890s, so those that already had them stuck with them and those that didn’t went for something else.

If I had to guess why 7.7 specifically it likely had to do with already making that size bullet and barrels.
 
The Japanese Army and Navy both passionately hated each other and had their own air units and arms procurements, keep that in mind for below section.
.303 British was in use from 1918 with purchased guns, new guns made chambered in it in 1932 (Type 92 and 97 aircraft MG's for Navy)
7.7x58 Semi-rimmed was the Army solution, it was a 162 grain bullet for Army ground (vehicles) and air use in 1930 (Type 89 air or ground)
7.7x58 Semi-rimmed was changed to a 204 grain projectile for use in the Type 92 machine gun, scaled up from the Type 3 which was in 6.5. Both hotchkiss variants with feed strips. This was in 1934, specifically done for longer range performance
7.7x58 rimless was developed for better feeding in box magazines for the Type 97 tank machine gun in 1937.
Finally, 7.7x58 rimless had ANOTHER slight dimension change and went from a 204 grain to a 182 grain projectile for use in Type 99 Arisaka rifles and LMG's, this was in 1940. This lighter bullet was to make it more managable for a shoulder rifle but keeping the standard cartridge.
Rimless and rimmed 7.7 had some interchangability but depended on the specific gun...

AP, Tracer and Incindiary existed for the .303 and 7.7x58SR and 7.7x58 rimless by 1930 for the heavier machine guns, so this may be why special 6.5 round development was less important.
6.5x50SR Arisaka was 139 grains at 2500 feet per second gave 2670 Joules on target
182 grain 7.7x58 at 2400 feet per second gave 3144 Joules on target
204 grains 7.7x58SR at 2500 feet per second was up to 3712 joules.

Even the weaker 7.7 rounds had about 18% more energy than 6.5x50SR. In certain roles like aircraft use that makes sense I suppose but what a logistical nightmare for them to change in 1940.
 
I think it all comes down to machine gun ammo like others have said. Logistically you want the same ammo for your rifle and MG. And the MG use is priority.

This is why the US stayed with the 30-06, zie Germans with 7.92, and the commonwealth -well 303 is a crappy rifle and MG round - but they probably just had too much stuff from WW1 stockpiles, too stingy to invest in a new caliber.

So the major powers had over powered rifles, because nobody wanted a separate smaller round for the rifleman. The adoption of the 5.56 M16 in the US changed all of that. When the US went to 5.56 for their rifle round, kept 7.62 for the M60 machine gun, and made it work then nobody looked back.

It will be interesting to see, now the the US is going to a larger caliber for their rifle to defeat body armor, if they have plans for their MGs to go a bit heavier too.
 
sledge said:
I think it all comes down to machine gun ammo like others have said. Logistically you want the same ammo for your rifle and MG. And the MG use is priority.

This is why the US stayed with the 30-06, zie Germans with 7.92, and the commonwealth -well 303 is a crappy rifle and MG round - but they probably just had too much stuff from WW1 stockpiles, too stingy to invest in a new caliber.

So the major powers had over powered rifles, because nobody wanted a separate smaller round for the rifleman. The adoption of the 5.56 M16 in the US changed all of that. When the US went to 5.56 for their rifle round, kept 7.62 for the M60 machine gun, and made it work then nobody looked back.

It will be interesting to see, now the the US is going to a larger caliber for their rifle to defeat body armor, if they have plans for their MGs to go a bit heavier too.
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Commonwealth tanks, or at least British tanks in WW2, had 7.92mm MGs too right?


If the reason for the change was "poor performance in China" is there a source on that, or exactly what the poor performance was?
 
Joel said:
Commonwealth tanks, or at least British tanks in WW2, had 7.92mm MGs too right?


If the reason for the change was "poor performance in China" is there a source on that, or exactly what the poor performance was?
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Yes that is correct , the Brits used the BESA mg , chambered in 7.92 mm , a Czech designed weapon
 
Another thing to consider with the 6.5 bullets used by most nations is that they were long torpedo style bullets. Extremely stable with huge penetration, but not much expansion or tumbling. Its part of the reason cartridges like 6.5x54 was used for elephant hunting as they could penetrate far enough to kill a elephant if you placed your shot right. The side effect of a bullet like that is I suspect a lot more wounding than killing as if you don't hit a vital your much more likely to simply have the round pass straight through.
 
And an extra mm of bullet is going to kill if you're hitting people in non-vital anatomy in the first place?

I mean, I get the reasoning if its something like a 303 Brit with the Mark 7 projectiles with the wood or aluminum in the nose so the bullet starts to violently tumble...

But how's a pass through with a 7.7mm gonna be any different from a pass-through with a 6.5mm if you're not hitting vitals, and gonna turn that into a kill somehow?
 
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