SMGs in ww2 with much smaller cartridges?

... instead of what was used historically.
So the USA and UK use something of .30 cal, Germans and Italians go down to 7-8mm, Soviets down to 6.5-7mm etc. If someone feels adventurous, even a .22 cal is in the play (but something powerful, of perhaps 500-600J muzzle energy when fired from a SMG barrel (~20 cm length); a number of countries were maing training rifles in .22 cal, so the barrel making hardware is already around.

How this influences the design of SMGs? Firing accuracy with lower recoil? Terminal ballistics (presumed the spitzer bullet is in use, at least for the .22)?
More rounds can be carried for the same weight, so this is at least one benefit.

Well, the two countries that tried changed their minds afterwards, or at least France did, Japan wasn't given a choice.

A real problem is that armies is WW II didn't have a warehouse of guns to be issued according to the day's mission.
If you had a lot of close quarters (buildings) guns and then you had to advance (or retreat) into the countryside the close quarters guns could be a real problem.
22LR Hi-Speed has around 100 joules at 200 yds. Down from just under 250 at the muzzle.

Or

At 200 yds the blue line is a little more than 1 meter low, at 250yds it is 2 meters low.
Wind drift is huge. If you only have one SMG per 8-12 man squad no big deal, But if you issue more per squad you have a really short range squad.

And the lower power bullets turn concealment into cover.
A 9mm may penetrate 3-6in of wood ( a lot depends on the type of wood).
Pre WW II ballistics charts show penetration at 15ft in 7/8in soft pine boards (dried) which may give the most penetration.
9mm Luger was good for 10-11 boards.
7.63 Mauser (Russian 7.62) was good for 11 boards.
.45 ACP was good for 6 boards.
The .45 ACP was not a good sub machine gun round.
The US would have been better using a slightly modified .38 Colt super speed ( get rid of the rim) for a 130 grain bullet at 1300fp out of a 5in barrel.
Think 9mm Mauser export.
.380/9mm Kurtz is good for about 5.5 boards and ballistics at longer range truly suck.

Shortround6 said:

A real problem is that armies is WW II didn't have a warehouse of guns to be issued according to the day's mission.
If you had a lot of close quarters (buildings) guns and then you had to advance (or retreat) into the countryside the close quarters guns could be a real problem.
22LR Hi-Speed has around 100 joules at 200 yds. Down from just under 250 at the muzzle.

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Please see this:

tomo pauk said:

even a .22 cal is in the play (but something powerful, of perhaps 500-600J muzzle energy when fired from a SMG barrel

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That will be something in-between the .22 WMR of the day and the .22 Spitfire.

Shortround6 said:

The US would have been better using a slightly modified .38 Colt super speed ( get rid of the rim) for a 130 grain bullet at 1300fp out of a 5in barrel.

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That works, too.

Ok, My mistake, I jumped to the 22LR.

tomo pauk said:

That will be something in-between the .22 WMR of the day and the .22 Spitfire.

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The .22 WMR of the day was the .22 WRF or .22 Remington Special.
Black powder cartridge only a bit more powerful than the .22LR although it could have been speeded up some.
But even the 1959 .22 WMR was a bit over 400 joules out of a 24in barrel so something more is needed.


There is not much saving using the .22 Spitfire as far as size/weight of weapon and the ammo. on about 120 rounds of ammo you can save about 1/2 kg.
The Spitfire may offer easier hitting out to 300 meters or so than the .30 carbine. And a lot easier compared to pistol caliber SMGs. Spitfire is about 1000-1100 joules.
Hot 9mm ammo is 650-700 joules (?)

Shortround6 said:

But even the 1959 .22 WMR was a bit over 400 joules out of a 24in barrel so something more is needed.

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Shortround6 said:

And a lot easier compared to pistol caliber SMGs. Spitfire is about 1000-1100 joules.

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These 1000+ J for the Spitfire is also from the long-ish barrel, almost 18 in.
The necked-down 7.63 Mauser of they day might do it perhaps?

Shortround6 said:

There is not much saving using the .22 Spitfire as far as size/weight of weapon and the ammo. on about 120 rounds of ammo you can save about 1/2 kg.

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The '5.56mm Mauser' might allow for carrying double the amount of ammo vs. the 9mm stuff, let alone vs. the .45 for the same weight?

What is perhaps more interesting is weapon development, that might saw the lighter SMGs, yet with better controlability in the automatic fire, and accuracy beyond 100m. Granted, a number of the ww2 SMGs were pretty controllable, from the Berreta to the Grease Gun.

tomo pauk said:

SMGs in ww2 with much smaller cartridges? ... instead of what was used historically.

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In most countries, the name for an SMG is "machine pistol", which best reflects the nature of this weapon. Pistol cartridges are already the smallest cartridges that armies have found effective and there is no room for reducing their energy. Smaller calibers require the creation of longer cartridges that do not fit in magazines in the grip of the weapon and longer barrels or high gas pressures. Lighter and faster bullets traveling at supersonic speed (twice the resistance than below the speed of sound) shorten the effective range of the weapon, and long ogives, which can improve the situation, additionally increase the length of the cartridges. Therefore, there is a practical gap between intermediate and pistol cartridges resulting from anatomy, the laws of physics and available materials.

tomo pauk said:

even a .22 cal is in the play (but something powerful, of perhaps 500-600J muzzle energy when fired from a SMG barrel (~20 cm length)

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So basically 5.7x28mm - a slight improvement in the weapon's accuracy at the slight cost of terminal effectiveness against unarmored targets.

tomo pauk said:

How this influences the design of SMGs?

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It doesn't. Pre-war submachine guns were not fully developed, and the weapon itself was of secondary importance.
During the war, SMGs were supposed to be cheap and operated by poorly trained conscripts.
Additionally, it was a weapon for enforcing obedience, for which a range was not required.

peceed said:

In most countries, the name for an SMG is "machine pistol", which best reflects the nature of this weapon. Pistol cartridges are already the smallest cartridges that armies have found effective and there is no room for reducing their energy.

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You will note that I'm not suggesting the reduction on muzzle energy vs. what was used in ww2 (machine) pistols.

peceed said:

Smaller calibers require the creation of longer cartridges that do not fit in magazines in the grip of the weapon and longer barrels or high gas pressures.

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People can make the bottle-necked cartridges, these were fitting even in the pistol grips historically.

peceed said:

Lighter and faster bullets traveling at supersonic speed (twice the resistance than below the speed of sound) shorten the effective range of the weapon, and long ogives, which can improve the situation, additionally increase the length of the cartridges. Therefore, there is a practical gap between intermediate and pistol cartridges resulting from anatomy, the laws of physics and available materials.

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Lighter and faster bullets travelling at supersonic speed were and still are the way to improve the effective range, not to decrease it.
It is always fancy when people make the 1st dibs on the laws of physics.

peceed said:

So basically 5.7x28mm

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Nah.

peceed said:

It doesn't.

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Or, it does.

tomo pauk said:

Lighter and faster bullets travelling at supersonic speed were and still are the way to improve the effective range, not to decrease it.

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As I mentioned, the 5.7x28 squeezes the practical maximum out of this concept (the real sweet spot), and the difference is so small that no army decided to change the caliber.
On the other hand, classic pistol ammunition occupies an interesting niche of subsonic ammunition.
In the USSR, the opposite move was made - the Tokarev 7.62x25 ammunition was replaced with the new Makarov 9x18mm.

peceed said:

As I mentioned, the 5.7x28 squeezes the practical maximum out of this concept (the real sweet spot)

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To what I've disagreed.

From left: Soviet 7.62x25mm, French 7.65mm Long, Japanese 8mm Nambu, British .380 Revolver, 9mm Parabellum (many nations),
U.S. .45 ACP and British .455 Webley.
The Soviet 7.62 was pretty much the same as the 7.63 Mauser. Depending on loading the Mauser is just about 400 Joules.
The French 7.65 has a 20mm long case and the US .30 cal Carbine has a 33mm long case.
Using smaller cases than existing pistol cases isn't going to work (except for the .45 ACP) even if you use a smaller bullet.
Maybe if you use a really long cartridge case but that sort of defeats the idea.
The old 7.65 Luger used a 93 grain bullet but saving 2 grams of bullet weight per cartridge doesn't really save that much. 250 rounds saves about 1/2 kg.

1923 Remington-Thompson In-house development for the M1921 Thompson SMG with a longer barrel for more power and range


since most everyone here is using Metric
11.4x25mm 440m/s with 16g bullet and 1580J energy

The later 45 Winchester Magnum had a 30mm case, but from a shorter barrel was 430m/s

A bit too powerful, and any .45 ammo is heavy

Now decades ago when I was doing more pistol shooting
I had a Colt Gold Cup in .38-45.
45 ACP necked down, for better feeding(for wadcutters) and accuracy. This was a 1960s Wildcat cartridge for target shooting,
as the 38 Super guns at the time had issues.

8.4g bullet, 380m/s and 600J

So flatter shooting, less recoil. slightly less ammo weight, and runs lower pressure than 38 Super for more life out of the firearm, while using existing magazines

Shortround6 said:

From left: Soviet 7.62x25mm, French 7.65mm Long, Japanese 8mm Nambu, British .380 Revolver, 9mm Parabellum (many nations),
U.S. .45 ACP and British .455 Webley.
The Soviet 7.62 was pretty much the same as the 7.63 Mauser. Depending on loading the Mauser is just about 400 Joules.

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Japanese and Soviets going down to 6.5mm might've been interesting (Japanese with also hotter loading than what their 8mm had). Granted, Soviets barrel-making equipment for the 6.5mm barrels is not something they had in spades in the 1930s, the ww1 Fedorov gun production notwithstanding.

Americans going down to the .38 Super, or the necked-down .45 would've also been interesting.

The most accurate official name for an SMG was the British 'Machine Carbine' which covers the ground inasmuch as the weapon was to perform the function of a carbine. Equally they made theirs to minimise production costs and weight. The Soviets followed the same route but went for folded steel sheet rather than welded and chose the same calibre as their rifle to be able to use the same barrel making as their rifle. Merely cutting shorter lengths off the long production rifled tubes.

Blowback is the simplest, cheapest and most reliable system but carries a limit in the mass of the bolt/ strength of the spring. Assorted delayed/locking breeches have existed but are unsuited to huge mass production and employing non firearms makers. As you push up the force of more powerful ammunition you inevitably have to increase the mass of the bolt to cope until it becomes untenable for the user or the rate of fire becomes ridiculous. 7.62x51 blowback rifles have been made but are very heavy and more a sign of desperation to make cheap construction and totally unsuited to the automatic fire vital to the machine carbine.

The Tokarev/Mauser Export 7.62x25 the Soviets chose is pretty well the power limit of a mass army Machine Carbine which can reliable feed in full automatic fire. One can tweak the bolt with denser metal inserts to save some volume and up the power with better powders. Short enough to make a handy magazine cross section and one might be able to tweak the bullet shape a touch but the 7.62x25 really is as good as you are going to get. Trying for more velocity requires smaller diameter bullets with spitzer pointed noses and maybe boat tailed bullets. Such bullets are fine for a formal rifle with a controlled feed but not for the feed out of a narrow magazine straight into the barrel. Feed reliability is a must in a Machine Carbine.

Essentially a small cartridge in any form is not going to enhance a Machine Carbine and we have seen the optimum in place in the 1930s and mass made since 1942. Since then we have seen what are really very short rifles taking on the role to fire from a locked breech not an open one at a far greater cost and for a limited role whilst the mass trend has been to literally make the infantry rifles shorter for the mass task with their smaller calibres.

So, to address the OP. No it would not have been any enhancement and the optimum was in mass use. Any smaller calibre tells one more about ammunition supply logistics and the user's standard existing pistol ammunition rather than a better Machine Carbine. The mass made blowback Machine Carbine is a mature design concept.

tomo pauk said:

To what I've disagreed.

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Your disagreement cannot change reality.
Practical pistol cartridges can no longer be longer, and wider cases reduce magazine capacity and require longer barrels in pistols or larger calibers, which again reduce range.
The Gordian knot can be solved by using pistol ammunition with a sabot, a great example of which is the 6.5x25mm CBJ.
The moment you give up pistol ammunition, there is no reason not to use intermediate ammunition, then you fall into the category of assault weapons.
The simplest solution to increasing the capabilities of submachine guns available to many sides of the war was to use 9x25mm cartridges, which allowed for the use of existing barrels and ammunition factories.
But increasing the range of the weapon was not worth the effort.

peceed said:

Your disagreement cannot change reality.

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That is true for everyone.
What is also true is that nobody here has a monopoly on being right on his assumptions. Both of us included.

Shortround6 said:

View attachment 804683
From left: Soviet 7.62x25mm, French 7.65mm Long, Japanese 8mm Nambu, British .380 Revolver, 9mm Parabellum (many nations),
U.S. .45 ACP and British .455 Webley.
The Soviet 7.62 was pretty much the same as the 7.63 Mauser. Depending on loading the Mauser is just about 400 Joules.
The French 7.65 has a 20mm long case and the US .30 cal Carbine has a 33mm long case.
Using smaller cases than existing pistol cases isn't going to work (except for the .45 ACP) even if you use a smaller bullet.
Maybe if you use a really long cartridge case but that sort of defeats the idea.
The old 7.65 Luger used a 93 grain bullet but saving 2 grams of bullet weight per cartridge doesn't really save that much. 250 rounds saves about 1/2 kg.

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The French 7,65 L was a copy of the .30 Pedersen.

A problem with necking down is that you get a slightly less efficient cartridge. You have a smaller "piston area" for the gases to push against.
Yes you can use a lighter bullet but that only goes so far.
A 110 grain .30 cal bullet has a sectional density of .166
A 75 grain .257 bullet has a sectional density of .162
An 85 grain .312 bullet has a sectional density of .125
A 60 grain .257 bullet has a sectional density of .130

Sectional densities are take from Hornady.
Very few (any?) bullet makers are making really light bullets in 6.5/.264 but the .257 are close enough.
A 90 grain .264 bullet has a has a sectional density of .184, very close to a .308 125 grain bullet.
Using pointy bullets, on either end, makes the bullet longer affecting either overall length or powder capacity (or both?). Maybe not a big deal given the bullets we are considering.

Necking the 7.62 Tokarev to 6.5mm is not going to get you much. An 86-90mm bullet is going to be a bit slower, even if more streamline and the lighter bullets, while a bit faster, are going to slow down quicker. Using a 75 grain bullet with a point on it, like a small 7.62 x 39 isn't going to do a lot compared to the standard round. Might be interesting to play with

I have been happy with the M-1 carbine, as were millions of G.I.s. Still in use in parts of the world. Remember, for those who like to waste lots of ammo, there is the M-2.

Sorry to sound like a doubting Thomas, but what problem are we solving here?

• 9x19 was at the time, and remains, an exceedingly successful set of tradeoffs. Perhaps we could make the case for the US to switch to it, in order to get away from the .45 and for achieving compatibility with the English.
• The modern 5.7x28 is perhaps a possible solution to what is presented in the original post (not sure what's wrong with that per Tomo's posts above), but the motivation for that seems largely to be ubiquitous body armor where pistol calibre doesn't cut it anymore. But that's no concern in the WWII era.
• Of all the military things the governments of the world had to plow down money into in the run up to the war, switching to a new pistol/SMG cartridge seems fairly low down on the list of priorities.
• If we want to invent the assault rifle a few years earlier, by all means do that, and that might replace a lot of SMG applications (not all though). But in that case we might be better off starting from rifle stuff rather than improving SMG's?

z42 said:

Sorry to sound like a doubting Thomas, but what problem are we solving here?

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Don't be sorry, I'm used that people are doubting a lot of my ideas
The ww2 SMGs as-is don't have some big problems, the biggest problem was that people were sometimes too late to introduce them, and in good numbers, in the second half of the 1930s.
What the small-caliber SMG might've offered is the lower recoil, accuracy beyond +-100 m, more ammo to be carried for the same weight. The SMG itself might've been lighter.