American small arms cartridges during WWII; why so little change?

[Interlinked]

IIRC it was a case of the technical commission concluding that the smaller cartridge was better, but the higher ups insisted on not losing any power.

7.62x51 was chosen because the Ordnance Board insisted that the new rifle must be no less "powerful" than the .30-06 fired out of a Garand. The only advancement achieved in the 7.62x51 cartridge was to slightly reduce the cartridge weight (by 2-3 grams) by shortening the case, which was possible because .30-06 had been designed for long boattailed M1 ball bullet. That was replaced by the flat-based M2 ball in the late '30s for range safety reasons.

7.62x51's trick was using a similar flat-based ball bullet as the design reference and just cutting off the case length that was no longer needed. Having a smaller volume, the powder burned at a higher pressure, and the M14 got the same muzzle velocity as the Garand out of a barrel shorter by 2 inches. The total weight savings for a rifleman from the new cartridge was like... 1 lb or 2 lbs or something like that, nothing serious.

[bojan]

Overall US small arms in WW2 were adequate (there was no real stinkers, and even much disliked M1919A6 was not horrible, just subpar compared to MG34/42 in LMG role), but their Co/Bn org with loads (for a time) of support weapons and propper logistic support would have made made almost any combo of small arms work. IOW, US could have stayed with 1903 and nothing fundamental would have changed in the course of WW2.

 

[RichTO90]

6 hours ago, Interlinked said:

IIRC it was a case of the technical commission concluding that the smaller cartridge was better, but the higher ups insisted on not losing any power.

7.62x51 was chosen because the Ordnance Board insisted that the new rifle must be no less "powerful" than the .30-06 fired out of a Garand.

No, it was MacArthur as Chief of Staff deciding that since the .30 caliber semi-automatic was considered feasible that it should be acquired instead so that the stocks of .30 caliber ammunition could be tapped. Ignoring of course that they could still be used in the existing M1917 MG and BAR. Gotta have commonality or some such. He was probably right though; I doubt that there was sufficient dollars for an entirely new cartridge and rifle, given the Army was having a hard time paying Christie. 😀

BTW, there was no "Ordnance Board" making that decision. There was the Ordnance Committee, which was represenatives of all interested parties making recommendations, but the CoS had the final say.

[RichTO90]

4 hours ago, bojan said:

Overall US small arms in WW2 were adequate (there was no real stinkers, and even much disliked M1919A6 was not horrible, just subpar compared to MG34/42 in LMG role), but their Co/Bn org with loads (for a time) of support weapons and propper logistic support would have made made almost any combo of small arms work. IOW, US could have stayed with 1903 and nothing fundamental would have changed in the course of WW2.

I agree. I do think that better use could have been made of the M1919A4, integrated into the Rifle Platoon as supporting the BAR-armed squads, but that did not fit the Army's Infantry doctrine.

[Interlinked]

8 hours ago, RichTO90 said:

No, it was MacArthur as Chief of Staff deciding that since the .30 caliber semi-automatic was considered feasible that it should be acquired instead so that the stocks of .30 caliber ammunition could be tapped. Ignoring of course that they could still be used in the existing M1917 MG and BAR. Gotta have commonality or some such. He was probably right though; I doubt that there was sufficient dollars for an entirely new cartridge and rifle, given the Army was having a hard time paying Christie. 😀

BTW, there was no "Ordnance Board" making that decision. There was the Ordnance Committee, which was represenatives of all interested parties making recommendations, but the CoS had the final say.

I admit I have no idea what the real history was, I'm just writing based on some comments written by someone else on a different forum. But I don't understand what you mean by commonality. 7.62x51 isn't reverse compatible with .30-06 guns without some sort of adaptor in the chamber, AFAIK. New cartridge meant new rifles and machine guns, or at least a costly refitment of legacy guns.

[R011]

32 minutes ago, Interlinked said:

I admit I have no idea what the real history was, I'm just writing based on some comments written by someone else on a different forum. But I don't understand what you mean by commonality. 7.62x51 isn't reverse compatible with .30-06 guns without some sort of adaptor in the chamber, AFAIK. New cartridge meant new rifles and machine guns, or at least a costly refitment of legacy guns.

I believe he meant commonality with pre-war .30-06 weapons.  The 7.62 x 51 mm Nato round came well after in the 1950s when the US was looking to replace all it's small arms.  The M14 was the M1 rifle, M1 Carbine, and BAR replacement while the M60 was the M1919A4 and A6 replacement.

Then the Air Force decided it wanted a lighter, smaller Carbine replacement than the M14 so they adopted the AR-15 which became the M16.

[Interlinked]

Oh then he meant what led to the Garand entering service, ok. 

[RichTO90]

2 hours ago, Interlinked said:

Oh then he meant what led to the Garand entering service, ok. 

I'm curious when you think that MacArthur was Chief of Staff? Yes, indeed, I was talking about 1932, not 1952.

[Interlinked]

33 minutes ago, RichTO90 said:

I'm curious when you think that MacArthur was Chief of Staff? Yes, indeed, I was talking about 1932, not 1952.

I assumed you were replying about 7.62x51 rather than talking about the origins of the Garand. I didn't write in reply to you, but to R011.

[RichTO90]

Never mind, I see you were talking about the M14 .30 caliber, where I was talking about the M1 .30 caliber. I thought your first sentence was addressing the decision on the M1, not the M14.

 

BTW, the M14 saved all of 0.9 pounds loaded versus the M1.

[seahawk]

19 hours ago, bojan said:

Overall US small arms in WW2 were adequate (there was no real stinkers, and even much disliked M1919A6 was not horrible, just subpar compared to MG34/42 in LMG role), but their Co/Bn org with loads (for a time) of support weapons and propper logistic support would have made made almost any combo of small arms work. IOW, US could have stayed with 1903 and nothing fundamental would have changed in the course of WW2.

 

The pressure for SMGs would probably have gone up with no semi-auto standard rifle.

But in the end all armies came up with basically similar ideas.

1. round for pistol and SMG

2. one round for rifle, MMG, co-ax

later most experimented with a medium round, when automatic/ semi-auto rifles/carbines became common

[Markus Becker]

On 7/3/2024 at 1:43 PM, bojan said:

Overall US small arms in WW2 were adequate (there was no real stinkers, and even much disliked M1919A6 was not horrible, just subpar compared to MG34/42 in LMG role), but their Co/Bn org with loads (for a time) of support weapons and propper logistic support would have made made almost any combo of small arms work. IOW, US could have stayed with 1903 and nothing fundamental would have changed in the course of WW2.

 

The BAR was IMO a but smelly because it was essentially the 1918 original. Fine for the time but a lot less so once you can have the FN D variant that's much easier to field strip. 

 

WRT .276 it was ~ like 7mm Mauser, development began before the Great Depression and the decision to use 30-06 instead was taken at the high of the Depression.

[rmgill]

8 hours ago, RichTO90 said:

Never mind, I see you were talking about the M14 .30 caliber, where I was talking about the M1 .30 caliber. I thought your first sentence was addressing the decision on the M1, not the M14.

Which M1 .30 caliber? Carbine or rifle? Or something else with a barrel 30 calibers long? 
 

I love the confusing nature of all the M1 items that are completely different. 
 

 

[RichTO90]

1 hour ago, rmgill said:

Which M1 .30 caliber? Carbine or rifle? Or something else with a barrel 30 calibers long? 
 

I love the confusing nature of all the M1 items that are completely different.

😁🤣😂

[Ivanhoe]

4 hours ago, rmgill said:

I love the confusing nature of all the M1 items that are completely different.

Everybody wants commonality, the Army developed model designator commonality.

 

[17thfabn]

On 6/22/2024 at 5:18 PM, RichTO90 said:

How many other nations besides Japan changed their pistol and rifle caliber standard before the war?

Italy? Tried to convert from 6.5 to 7.35 mm.

[RichTO90]

3 hours ago, 17thfabn said:

Italy? Tried to convert from 6.5 to 7.35 mm.

Yep. And how did that work out? At least Germany waited until it didn't matter to produce the 7.92mm Kurz.

[17thfabn]

On 6/22/2024 at 4:29 PM, Ivanhoe said:

why so little change in small arms cartridges?

.45 ACP, .30 Government (M1906, of course), .50 BMG, 20x110, 40mm Bofors, pretty much all in place before 1939. The US certainly had the industrial might to develop new cartridges, but TMK did not do so.

It is out side the scope you have laid out.

I would say from .45 cal up to 16 inch the one type of U.S. ammunition that could have used the most improvement was 75 mm, 76 mm 3 inch anti tank ammunition. 

Edited July 6 by 17thfabn

[17thfabn]

4 minutes ago, RichTO90 said:

Yep. And how did that work out? At least Germany waited until it didn't matter to produce the 7.92mm Kurz.

Are you asking me to defend Italy's attempted change over? 

[RichTO90]

5 hours ago, 17thfabn said:

Are you asking me to defend Italy's attempted change over? 

Nope.

[RichTO90]

5 hours ago, 17thfabn said:

It is out side the scope you have laid out.

I would say from .45 cal up to 16 inch the one type of U.S. ammunition that could have used the most improvement was 75 mm, 76 mm 3 inch anti tank ammunition. 

Yep. Any of Army Ordnance's AP and APC rounds could have benefited from improvement. The design and manufacturing methods and specifications for the projectile bodies were poor, as were the fuzes, windscreen, and penetration caps. The propellants produced too much smoke and flash as well, especially in the 76mm/3" until the improved long primer was introduced in late 1944. About the only decent thing was probably the explosive filler.

[Markus Becker]

On 7/6/2024 at 1:55 AM, RichTO90 said:

Yep. And how did that work out? At least Germany waited until it didn't matter to produce the 7.92mm Kurz.

Let's be fair to the Italians. They didn't expect a war to start before ~43 when they planned to caliber change. 

[17thfabn]

It is ironic that the two countries that attempted a caliber change over both used 6.5 mm.  In many studies 6.5 mm is believed to be about the perfect caliber for infantry rifles.

6.5 mm is such a perfect caliber that as far as I know, no modern military uses it as a standard issue caliber. 

From what I've read the Japanese 6.5 mm was considered to be an effective projectile. The Italian 6.5 mm on the other hand being a round nosed bullet could use improvement. Could the Italians 6.5 Carcano have been adapted to use a spitzer type bullet? Would this require modifications to the rifle to feed reliably? 

[Ol Paint]

On 6/30/2024 at 6:43 PM, RichTO90 said:

The Navy's submarines of the 1920s and into the 1930s were powered by Nelseco, Busch-Sulzer, and Hoover-Owens-Rentschler diesel engines. The Grey Marine and Fairbanks-Morse date from the late 1930s. The Grey Marine is a GM truck diesel and has nothing to do with the MAN submarine diesels. The Fairbanks-Morse does have a German connection, but not to MAN, rather to Junkers, and not to a submarine diesel, but rather to an aircraft diesel, the Jumo 205.

Minor correction:  The US submarines used GM Cleveland diesels, not Grey Marine, and share design lineage with the Winton/EMD locomotive diesel engines, not truck engines.  While Electro-Motive Corp (later Division) developed the 567 series engines to rectify issues encountered with the Winton 201A, Winton--later renamed Cleveland--would develop the 248 series followed by the 278 series.  EMC/EMD and Cleveland Diesel did share resources and Cleveland handled adapting the EMD 567 series for industrial and marine applications.

https://vintagedieseldesign.com/2019/12/07/cleveland-diesel-engine-division-gms-war-hero-turned-ugly-stepsister/

https://maritime.org/doc/fleetsub/diesel/chap3.php#3A

As you pointed out, the F-M engines do have a German (Junkers) root, but its unclear how much remained in the OP 38D 8-1/8 engines beyond the shared opposed piston configuration.  In addition to the displacement (Bore diameter is approximately double that of the Jumo 204 and Jumo 205 at 8.125" vs. 4.72"/4.13" and the stroke is similarly upsized at 10" compared to 8.27"/6.30", respectively, FM had moved to a vertical shaft timing drive instead of the Jumo spur gear train, and the crank timing appears to be different, as well.  Incidentally, the same basic engine is still on offer from Fairbanks Morse Defense:  https://www.fairbanksmorsedefense.com/solutions/engines/fm-38d-8-18  91 years and counting.

Doug

(As a completely off topic aside, F-M also still catalogs the Alco 251 diesel.)

 

[Markus Becker]

9 hours ago, 17thfabn said:

It is ironic that the two countries that attempted a caliber change over both used 6.5 mm.  In many studies 6.5 mm is believed to be about the perfect caliber for infantry rifles.

6.5 mm is such a perfect caliber that as far as I know, no modern military uses it as a standard issue caliber. 

From what I've read the Japanese 6.5 mm was considered to be an effective projectile.

 

They were at the time. The first wave of smokeless rounds were in the 7.5 to 8mm range and then almost everone adopted 6.5 or 7mm because with round nose bullets they were much flatter shooting.

After WW1 the trend went into the opposite direction because now everone had realized the critical role of machine guns and relative unimportance of rifles. At longer ranges - that you only get with MGs - the heavier round performs better. Thus the Japanese adopting 7.7mm and the Swedes and Italians introducing 8mm machine guns.

 

Quote

The Italian 6.5 mm on the other hand being a round nosed bullet could use improvement. Could the Italians 6.5 Carcano have been adapted to use a spitzer type bullet? Would this require modifications to the rifle to feed reliably? 

Acc to @bojan not really. Something with the twist rate of the rifling. It was easier to bore the barrrels out to 7.35mm. BTW, 7.35*51 is 128gr at 2.500fps. That's just a bit more than 7.62*39.