Reduced power 7-8mm cartridges post ww1?

[tomo pauk]

Japanese used the weaker loading on their post-ww2 7.62 NATO ammo, that was making just 700 m/s for a relatively short barrel (with the 'normal' bullet works to about 2340J?). Spanish were trying their weak-ish 7.62mm ammo, too, of some 2300J.
The better known and comparable - energy-wise - cartridges were good for 2390J (7.35mm Carcano) and 2450J (Czech 7.62).

The full-power, modern cartridges of the day were making between ~3200 to 4000J.

So for the needs of this thread, we'd have people coming to the firm conclusion that such the powerful cartridges are actually too powerful, especially with regard to the lighter automatic weapons, and explore the reduced-power versions of them that is still useful on the battlefield. The resulting weaker versions make between 2300 and 2500J. Each weapon needs to be proofed for the old, powerful ammo if that is existing, but that ammo is to be used in emergencies only, much like it was the case with the Japanese rifle.

French do this in the 7.5mm rimless, Americans do this instead of the .276 Pedersen, Italians move a bit faster with the 7.35 etc. This scenario changes the design of the infantry guns in the 1930s-40s by a good amount.

Yes, going full-on with intermediate cartridge would've been even better, but this is not it's scenario

 

[Shortround6]

What are you giving up?
The reduced power cartridges are not going to work in most medium/heavy machine guns.
By work I mean do the job the army/s want them to do (long range fire) not just get the guns to fire in a reliable manner.

Where the crossover occurs may depend in the power of the reduced power/intermediate cartridge.
The medium/heavy machine gun was a large part of the infantry battalions fire power in the 1920s and 30s. 3in/81mm mortars had not really shown up in quantity during that time period. British battalions didn't even have heavy machine guns. All the Vickers guns belonged the the Machine Gun Corp and companies/platoons were assigned to Brigades/regiments/battalions as needed (although they often were semi-permanent)

The Soviets adopted a belt fed RP-46 version of the DP-28 in 1946 for a company support weapon even with the SKS, AK-47 and the RPD belt fed light machine gun.
The RP-46 was replaced by the PK machine gun so the old 7.62 x 54R was never totally replaced by a reduced power round.

Italians adopted a powerful 8mm round for their tripod and AFV machine guns. So did the Swedes. Swedes even built Mauser rifles using the MG round so the machine gun crews only had to deal with one type of ammo.
Japanese moved from the 6.5 Arisaka to the 7.7mm round for rifles and MGs because they were not happy with the 6.5mm round for machine gun use.

If you are happy with a two round solution then the reduced power round does have a number of things going for it. If you want to keep a one round solution for logistics you are stuck (sort of) with an over powered round for rifle use.

The US actually did this (sort of) with the M1 rifle. The gun was proofed for the M1 round which used a 172 grain bullet that gave over 1000yds more range than the old 1906 load used in the 1903 bolt gun. In the late 30s the 1906 load was replaced by the M2 load which used a new powder at lower pressures to have the same velocity/ballistics as the 1906 load in the rifles. The M2 load was preferred in the M1 rifle compared to the heavy bullet M1 load because it battered the gun less and had a lesser tendency to bend the operating rod (gas piston). Nobody thinks the M2 load was a reduced power load

Problems come in with trying to use the reduced power loads in machine guns. They sometimes will not operate the gun when dirt/debris is present. And long range performance is lacking. On the flip side, while you can use the higher power ammo in the rifles without blowing them up, they do were out/break sooner.
Some/many gas operated guns have adjustable gas ports/blocks to allow for different power ammo to be used. But this requires more cost in manufacturing and better training.
Recoil operated guns are very hard for users to adjust. In the 1950s there were some attempts to use "self regulating" gas systems. Short stoke pistons that dumped the pressure after a short piston travel. This helped but was not a sure cure. Dirty guns often needed more than the sharp initial impulse to keep running.
Bren guns had a four port system to increase gas pressure to keep the gun running. With a clean gun you could have used the two bigger ports to get the gun to function but you are running out of options when things go bad.

 

[tomo pauk]

What are you giving up?
The reduced power cartridges are not going to work in most medium/heavy machine guns.
By work I mean do the job the army/s want them to do (long range fire) not just get the guns to fire in a reliable manner.

I'm not giving up a lot.

Americans were designing the Garand rifle and Johnson LMG. These two with a less powerful cartridge means that the new rifle can be 2-3 lbs lighter than the historical type, while the Johnson LMG will be less of a beast towards the user's shoulder. Make the new BARs and M1919s for the L-P cartridge.
British were buying the future Bren gun. So no change for them, apart that the Bren can be lighter, or it can longer sustain the firing before the barrel needs to be changed. Same for the Vickers GO.
Germans were designing the MG 34. Again, can be lighter this time 'round.
French were making the new round and weapons for it anyway, so no bad consequences for them either. Same for Italians.
Soviets can have an easier time in making their self-loading rifles.
All of these countries can make the manually-operated carbines now, without having to deal with the heavy recoil and muzzle flash if the full powered cartridge is used. Also all of them can use the legacy bolt-action rifles to fire the new ammo.

It is not required for either of these countries to destroy the older ammo stocks.

 

[Shortround6]

It is not required for either of these countries to destroy the older ammo stocks.

The question is not destroying old stocks but having to make new stocks incase of war.
I am a big fan of reduced power cartridges for shoulder weapons.

Americans were designing the Garand rifle and Johnson LMG. These two with a less powerful cartridge means that the new rifle can be 2-3 lbs lighter than the historical type, while the Johnson LMG will be less of a beast towards the user's shoulder. Make the new BARs and M1919s for the L-P cartridge.
British were buying the future Bren gun. So no change for them, apart that the Bren can be lighter, or it can longer sustain the firing before the barrel needs to be changed. Same for the Vickers GO.
Germans were designing the MG 34. Again, can be lighter this time 'round.

Actual weight reductions are going to be a lot less than 20-30%. You are stuck with 1920/30 metallurgy/technology.
For example the Pederson rifle weighed 4.1kg, the Garand weighed around 4.7 kg. Some were as light as 4.3 some over 5kg.
No aluminum receivers and few, if any, sheet metal receivers on service rifles. Some of the weight can be blamed on the wood stocks. Unless you reduce the size (length) of the stocks significantly you are stuck with the weight of the wood. Armies had had several centuries to figure out what wood to use in stocks to keep breakage to a minimum.
Now the problem in 1930s for the US was that they were NOT going to go to a low powered cartridge for the 1917 and 1919 machine guns.
The tripod mounted machineguns were the long range firepower of the battalion. Unless you come up with new weapons (and man power) and/or better signaling for artillery support.
In fact the 1919A4 (the common version in WW II) was not adopted until 1936 with low scale production for the first few years. The 1919 had been designed for tank use and the 1922 version (the A2) used a short light barrel for cavalry use (carried on horse back) but the short light barrels hurt reliability.

The move to lighter weight guns post WW II coincided with much greater numbers of radios allowing for much better artillery support. More motor vehicles (in armies aside from the US and UK) carrying more ammo. In the west the US 105mm howitzer became the De facto NATO light artillery gun. Infantry units could be biased more to short range firepower with much more assurance that long range/heavy support was available in a timely fashion.
The US had adopted the French Brandt 81mm mortar in the early 30s but production may have been slow. Doctrine may have been slow in coming. It didn't help that the US adopted both light and heavy bombs and the heavy bomb only ranged to 1275yds(?) in the initial version, leaving just the light bomb (3.2kg) and machinegun fire for long range (1200-2400yd) use.
In the summer of 1941 with zero combat experience the US army was planning on carrying in a Regiment the following ammo.
8250 rounds per 1917 machine gun
6000 rounds per 1919 machine gun
2800 rounds per .50 machine gun (listed as anti-tank machine gun)
300 rounds of 37mm ammo per gun (90%AP; 10% HE)
300 rounds of 81mm per tube (70%HE light, 10% HE heavy, 20% smoke)
220 rounds of 60mm per tube (100%HE)
28 rounds of .45 pistol.
1720-1748 rounds for each BAR
328 rounds for each M1 rifle
220 rounds for each 1903

These are the ammo totals for the individual armed with the weapon/s or on the prime mover or ammo truck + in the unit ammunition train + ammo train of higher unit.
The .30 cal Brownings are listed has having an effective range of 3000 yds with the 1906/M2 ammo and 4000yds with the M1 ammo (boat tail ball 172-174 grains)
The shoulder rifles and the BAR are all listed as having 600yd effective range regardless of the ammo. Yes their ammo was over powered.

WW II experience would show that the long range machine gun had already had it's day, but radio usage was rapidly increasing from late 1942 onward.

But trying to back date this to late 20s or early 30s calls for changes in doctrine and tactics and communications and logistics.
The US didn't get the first 105 howitzers until 1940, Infantry divisions had 75mm field guns.

Other nations can trace similar histories. British issued tripods to company HQ to be issued for defensive use or for firing at long range for the Bren guns. They probably got lost after weeks/months of movement. Brens had quick change barrels. Issue 3rd barrel for sustained fire rather than hurt long range fire.
MG-34, again an optional tripod mount for long range fire and quick change barrel

Quite a bit of kit for long range fire. All or most kept for the MG 42. and the concept was retained for the MG 3 in the 1950s and later.

The reduced power cartridge is a good idea, but it pretty much forces the adoption of a two cartridge solution.
Now wither that solution is executed within the squad or at higher level (company?) is a good question.
British riflemen sometimes acted as ammo carriers for the Bren gun, refilling Bren magazines for the gunner/s with their rifle ammo.
Other nations did the same thing. Japanese planned one of their guns to use a hopper using rifle clips. Unfortunately the gun did not like full power ammo and wound up needing it's own cartridge supply.

 

[tomo pauk]

The question is not destroying old stocks but having to make new stocks incase of war.

Making of the new stock of ammo is not forbidden.

The .30 cal Brownings are listed has having an effective range of 3000 yds with the 1906/M2 ammo and 4000yds with the M1 ammo (boat tail ball 172-174 grains)
The shoulder rifles and the BAR are all listed as having 600yd effective range regardless of the ammo. Yes their ammo was over powered.

Effective range should mean that something can be actually hit. 4000 yds with the M1 ammo is almost double the effective range of 'my' Czech 30mm against the ground tartgets, so I'd have the same drink that the man that can do 4000 yds drinks

Now the problem in 1930s for the US was that they were NOT going to go to a low powered cartridge for the 1917 and 1919 machine guns.
The tripod mounted machineguns were the long range firepower of the battalion. Unless you come up with new weapons (and man power) and/or better signaling for artillery support.
In fact the 1919A4 (the common version in WW II) was not adopted until 1936 with low scale production for the first few years. The 1919 had been designed for tank use and the 1922 version (the A2) used a short light barrel for cavalry use (carried on horse back) but the short light barrels hurt reliability.

US Army can test out the waters wrt. just at what distance the new cartridge, when fired form a tripod-mounted MG, can kill an enemy. They can also test the new BAr vs. the old BAR, and see how much of difference is actually there.

British riflemen sometimes acted as ammo carriers for the Bren gun, refilling Bren magazines for the gunner/s with their rifle ammo.
Other nations did the same thing. Japanese planned one of their guns to use a hopper using rifle clips. Unfortunately the gun did not like full power ammo and wound up needing it's own cartridge supply.

Soldiers can still carry the same ammo as what the Bren used, since they will also use the same ammo.

 

[tomo pauk]

The reduced power cartridge is a good idea, but it pretty much forces the adoption of a two cartridge solution.

A bit to elaborate on this.
French - they introduced a new cartridge historically, without making a new tripod-mounted MG for it.
Americans - less of the change than what was supposed to happen with the introduction of the .276 Pedersen.
Italians - no change vs. what happened historically, bar that a bit greater push is supposed to happen with the 7.35 mm. Kill off the 8mm Breda to help out.
British - they introduced another RCMG cartridge in the late 1930s, creating the two cartridge situation without my help

 

[marathag]

French do this in the 7.5mm rimless, Americans do this instead of the .276 Pedersen, Italians move a bit faster with the 7.35 etc. This scenario changes the design of the infantry guns in the 1930s-40s by a good amount.

On the US Side, there was the ever popular 30-30 Winchester, the 303 Savage and its rimless competitors the 30 Remington and 300 Savage on the civilian side.
That range in power from 2000J to 3500L, with case lngths from 48 to 52mm and base diameters from 10.7-12mm

 

[tomo pauk]

On the US Side, there was the ever popular 30-30 Winchester, the 303 Savage and its rimless competitors the 30 Remington and 300 Savage on the civilian side.
That range in power from 2000J to 3500L, with case lngths from 48 to 52mm and base diameters from 10.7-12mm

Food for another thread

 

[marathag]

Food for another thread

For actual popgun loads on the 30-06, I have reloaded M1 Carbine bullets and 4227? powder that were around 1500fps so I could fire my Springfield all day long and not get beatup badly by it

 

[Shortround6]

Effective range should mean that something can be actually hit. 4000 yds with the M1 ammo is almost double the effective range of 'my' Czech 30mm against the ground tartgets, so I'd have the same drink that the man that can do 4000 yds drinks

All the machine gunners were trying to do was get bullets into a patch of ground to deny the enemy from transiting the area (reinforce, supply, retreat) not hit individual targets.
Basically suppression. And since they could put bullets into small fields at a distance that their own 81mm mortars could not even reach, it was judged worthwhile. Maybe you needed 3-4 guns (or more?) to do it but trying to get divisional artillery support in the 1930s could take a while or they were busy doing something else.


For some reason many countries just bypassed small diameter boat tail spitzer bullets. I don't know why. They had built long skinny round nose flat base and shorter Spitzer flat base.
The US and France and Germany and Britain had built 7.62-8mm boat tail bullets for machineguns. I don't know why they didn't do the same thing for the 6.5-7mm bore sizes,
And without such bullets you don't get the needed long range ballistics. The US got lucky, they had designed the old .30-03 round (original 1903 rifle round) to use a 220 grain round nose bullet and needed a 1 turn in 10in travel twist in the barrel to get it to work. They didn't change it for the .30-06 round with the 150 grain spitzer at much higher velocity. Turned out that it worked quite well with the 1919/M1 spitzer boat tail bullet. No change in rifling needed. With the 7.62 NATO they changed the rifling twist to 1 turn in 12 in of travel. Gave a small bit of extra velocity with the 150 grain flat base or 147 grain slight boat tail or? But they don't like long pointy bullets at long range (1000yds). But the need for machine guns to fire at 2000+ yds had disappeared.
You can make 6.5 bullets shoot just fine at long ranges, but you need the right rifling twist to do it and you need good bullets. Between the wars the .25 cal hunting rifles got a bad reputation in the US for accuracy. Many hunters are lucky they get the big end of the rifle on their shoulders let alone understand ballistics (either internal or external).
There was nothing wrong with the bore size or barrels/rifling. What they were dealing with was poor quality control in some of the bullets. The jacket material was not of uniform thickness which put the core off center in the finished bullet which made the bullets wobble around the actual center of gravity. A lot of bullets use the same jacket thickness regardless of the diameter of the bullet (within limits) and the smaller the diameter of the bullet the greater percentage of the diameter the jacket takes up and the more off center the core can be percentage wise. Skinny bullets with long noses and boat tails need more twist than shorter blunter bullets of the same weight (needed twist is based on the length of the bullet, not the weight).

You can get a 120-130 grain 6.5mm bullet to act like a 172 grain 7.62 bullet at long range as far as trajectory and wind drift goes. You can get a recoil reduction in proportion to the bullet weight. You can also get an impact energy importation to the bullet weight (and better than a 150 grain 7.62 flat base).
What you may have trouble with is bullet fabrication and perhaps just as important, convincing some generals that small bore rifles will do the job (wounding/killing).
The Italians and Japanese with their 1930s war experience were not convinced but they were using (mostly) long skinny bullets that were rather stable. The Spitzer bullets had greater tendency to turn sideways.

 

[tomo pauk]

The US and France and Germany and Britain had built 7.62-8mm boat tail bullets for machineguns. I don't know why they didn't do the same thing for the 6.5-7mm bore sizes,

Perhaps that had a lot to do with the lack of 6.5-7mm military cartridges (bar one-offs, small batches and experiments) in these countries

You can make 6.5 bullets shoot just fine at long ranges, but you need the right rifling twist to do it and you need good bullets. Between the wars the .25 cal hunting rifles got a bad reputation in the US for accuracy. Many hunters are lucky they get the big end of the rifle on their shoulders let alone understand ballistics (either internal or external).

6.5-7mm cartridges introduced by the big players in the 1930s is the food for another thread

 

[Shortround6]

A bit to elaborate on this.
French - they introduced a new cartridge historically, without making a new tripod-mounted MG for it.

Just about the worst cartridge shape ever to try to use an a repeating rifle let alone an automatic.
Had they had the budget for it I am sure a new heavy machine gun would have been developed.
And the French 7.5 was in no way, shape or form a low powered cartridge.

Americans - less of the change than what was supposed to happen with the introduction of the .276 Pedersen.

Not sure about this, the Americans had introduced the two different cartridges back in 1919 with the higher powered machine gun ammo vs the standard bolt action rifle ammo.
You could use either round in either gun but you really had to pay attention the sights. The M2 ball ammo was identical in ballistics (and recoil) to the old 1906 ammo.

Italians - no change vs. what happened historically, bar that a bit greater push is supposed to happen with the 7.35 mm. Kill off the 8mm Breda to help out.

Killing off the 8mm Breda kills off the Italian long range machine gun. The 7.35 was a terrible long range (or even medium range) round.
Ballistically it is very close to the 1950s 7.62×45mm Czech cartridge. A bit better than the 7.62 x 39 but the use of short light semi streamline bullet kills the long range performance.
Getting rid of the 8mm Breda would have been a benefit to the British/commonweath forces in NA.

British - they introduced another RCMG cartridge in the late 1930s, creating the two cartridge situation without my help

They might have transition to the 7.9mm Mauser given enough time. They were not happy with the .303 in automatic guns.
But they were not looking at lower powered rounds.
They figured by keeping the 7.9mm ammo in the armored forces they were somewhat simplifying the ammo supply.

 

[tomo pauk]

Had they had the budget for it I am sure a new heavy machine gun would have been developed.

Maybe, maybe not.

And the French 7.5 was in no way, shape or form a low powered cartridge.

Of course.

Not sure about this, the Americans had introduced the two different cartridges back in 1919 with the higher powered machine gun ammo vs the standard bolt action rifle ammo.

I am sure that they were very serious about the Pedersen round

Killing off the 8mm Breda kills off the Italian long range machine gun.

Getting rid of the 8mm Breda would have been a benefit to the British/commonweath forces in NA.

Italians were making the MGs for the .303 British in the interwar period. Make a heavy barreled SAFAT machine gun for the infantry and you're set, without investment in the new cartridge, MG type and all-new barrel-making tooling.

They [British] were not happy with the .303 in automatic guns.

Was that really the case?

 

[Shortround6]

6.5-7mm cartridges introduced by the big players in the 1930s is the food for another thread

But it helps explain the lack of enthusiasm for the low powered 7-8mm rounds.
Light, short/blunt 7-8mm bullets lose velocity/energy faster than heavier, long bullets.
You start out with less power and the difference in power (and trajectory) gets worse as the range gets longer.

You have better fire power at close ranges but things go to crap at long ranges.

There were a couple of charts in the first edition of Jane's infantry weapons (page 180-181) that showed expected ranges of rifle and machine guns.
Sadly for the American notion of long range riflemen it shows for rifles
30% of all engagements at 100 meters or less.
72% of all engagements at 200 meters or less.
88% of all engagements at 300 meters or less.
97% of all engagements at 400 meters or less.

However the chart for the machine gun shows that 50% of all engagements are at 750 meters or less.
20% of all engagements at 400 meters or less.
40% of all engagements at 600 meters or less.
81% of all engagements at 1200 meters or less.
95% of all engagements at 1600 meters or less.

These are supposed to be US figures but it doesn't say what time period/s were used (which wars).
Maybe the statisticians had an agenda (book is from 1975 and the stupidity of US small arms development was in full flower in the 60s and 70s).
Restricting your squad automatics/machine guns to low powered rounds was found to be a major disadvantage in some of the wars from 1991 on causing a mad scrabble to get old "obsolete" guns out of storage and to the active combat zones.

Now there are the actual terrain factors to consider. If you can pretty much guarantee operating in urban areas, forests, jungles you can get away with shorter range weapons. If you are fighting in open areas (deserts, grass lands, large cultivated areas) you can have problems.

 

[Shortround6]

Was that really the case?

The British were not happy with the .303 before WW I.

British Military Small Arms Ammo - .256 & .276 inch Ball

One of the many lessons learned during the Second Boer War in South Africa was that the .303 inch cartridge was lacking in terms of velocity and accuracy compared to the 7x57mm Mauser round used by some of hte Boers. The .303 inch Short Magazine Lee Enfield had been adopted in 1903 but was not

sites.google.com

Unfortunately they listened to the target shooters a bit too much.
Using a big case and small bore was problem with the existing powders of the time (still a problem, just not quite as bad)
Just trying to get .303 to stack in magazines was problem (and using drums like the Lewis was more of a crutch than a good solution).

Money dried up after fighting stopped in WW I and by WW II they had a better idea of what they wanted, they just had to pay for everything else.

 

[tomo pauk]

The British were not happy with the .303 before WW I.

We're now a whole Great war worth of the bloodshed in the future.

Just trying to get .303 to stack in magazines was problem (and using drums like the Lewis was more of a crutch than a good solution).

Seems like it worked in the Bren, and indeed in the pan magazines.
It also worked in the belt-fed MGs.