FG 42, but designed around a non-German cartridge from day 1

[tomo pauk]

The historical FG 42 was designed around the rather stringent requirements, that stipulated use of the full-power cartridge in a hand-held weapon that is not heavier than 5 kg, the weapon being capable for the automatic and single-bullet fire.
It is my understanding that FG 42 ended up as a very good weapon (with almost cult-like following today), with the shortcomigns being that was expensive to make, and that the muzzle blast was sizable, to say at least.
So let's make it different this time - designers are allowed to use an existing non-German rifle cartridge, provided that the cartridge and an the initial number of barrels are easily available for Nazi Germany of the late 1941/early 1942. Cartridge does not need to be as powerful as the 7.92x57. The alternative FG 42 is not expected to be made in millions anyway like it is the case when the major change of regular infantry weapon change (here is about the thousands of weapons needed), so the logistics are not that demanding as it will be in that case.
The non-German cartridge used can be as-is, or with a bit of nip and tuck to fit better the new weapon; in the later case, it is required that original cartridge can still be used need-be. Weapon is still required to be able to do the automatic fire, while weight is to be up to 5 kg. At least 20 cartridges in a removable magazine, as per historically.

What cartridges might be the best choice, that can still make weapon useful at longer ranges while not 'beating' the weapon internals and the soldier using it? Lower powered cartridge should be making the smaller muzzle blast, and the automatic fire will be more controllable, but it might be worse off against the targets past, say, 500 m?

Impact on the development of the self-loading and/or automatic weapons after 1943?

 

[ssnider]

post war Swiss effort


View: https://www.youtube.com/watch?v=HCXtUQkXlxY

 

[Shortround6]

6.5 Carcano
6.5 Arisaka
6.5 Mannlicher
with pointy bullets 120-130 grains (7.8-8.4 grams).

A problem with the FG 42 spec was that it was supposed to somewhat replace the MG 34/42 and needed longer range than the intermediate cartridge that was used in the MP-43.
The suggested bullets will mimic the trajectory of the 7.9mm well enough well past 500 meters. A 120 grain bullet will give 20% less recoil than the 7.9mm at the same velocities.
Adjust as desired to cut down muzzle blast vs long range trajectory. You can use a somewhat shorter and/or skinner case to get the velocity compared to the 7.9 X 57 case.

Using a shorter/lighter 7.5-7.9mm bullet hurts long range performance.

 

[z42]

6.5 Carcano
6.5 Arisaka
6.5 Mannlicher
with pointy bullets 120-130 grains (7.8-8.4 grams).

A problem with the FG 42 spec was that it was supposed to somewhat replace the MG 34/42 and needed longer range than the intermediate cartridge that was used in the MP-43.
The suggested bullets will mimic the trajectory of the 7.9mm well enough well past 500 meters. A 120 grain bullet will give 20% less recoil than the 7.9mm at the same velocities.
Adjust as desired to cut down muzzle blast vs long range trajectory. You can use a somewhat shorter and/or skinner case to get the velocity compared to the 7.9 X 57 case.

Using a shorter/lighter 7.5-7.9mm bullet hurts long range performance.

6.5 Swedish

IIRC a number of studies have been made over the years, coming to the conclusion that the best (as in, compromise between weight, recoil, ballistics, and hitting power) military rifle caliber (and accompanying squad MG) would be a full power cartridge in the 6-7mm range with a long boat-tailed bullet.

Post-WWII both the Western and Soviet blocs chose expediency leading to the 7.62x51 and 7.62x39, respectively. And then the pendulum swung in the other direction, leading to the adoption of the 5.56/5.45mm systems.

 

[Shortround6]

The 6.5 Swedish would work but the cartridge case is larger than needed.
You can get the performance desired with a shorter, skinner case.

 

[tomo pauk]

6.5 Carcano
6.5 Arisaka
6.5 Mannlicher
with pointy bullets 120-130 grains (7.8-8.4 grams).

6.5 Swedish

Indeed, the different 6.5 mm cartridges make a lot of sense here, especially when looking back from today's era.
The 6.5 Swedish was also a Norwegian cartridge, and the 6.5mm was both Austrian and Dutch cartridge, so either will be easily available in Germany of late 1941. All of the European 6.5mm types will indeed need the spitzer bullet to work well.
BTW - Wkipedia does not note that there was a spitzer bullet for the Norwegian 6.5mm, but the German data plates do (9g bullet, velocity V25 of 745 m/s ) - ie. a bit weaker than the Swedish spitzer, but here this can be an advantage.

I wouldn't worry too much about a few mm of difference, after all the FG 42 worked with the long German cartridge.

I was trying to find the merit for the more powerful cartidges for this task, such are the 7.5mm French or the 7.65 Belgian (both being very modern for the day), but choosing these offers just minor saving in the forces for the weapon to withstand, so Germans might as well and go with the historical bullet.

Another cartridge that was pretty 'mild' when compared with the 7.92x57 was the Italian 7.63x51. With just under 2400 J, it is under the Arisaka's ~2670, let alone the big ~4000J of the 7.92. Italians were under pressure to miliatrize fast, and the 7.35mm stuff just didn't had enough of wherewithal to replace the 6.5mm, so they might be grateful for a shipment of, perhaps, French infantry weapons & ammo to the units in N.Africa in exchange for shipping the 7.35mm ammo & barrels to Germany. When compared with some 6.5mm cartridges, it is already with the spitzer bullet.
Yes, the 6.5mm cartridges with spitzer bullets will outperform it as the distances increse.

FWIW, here is Gun Jesus, and hi's opinion about the 7.35x51 might surprise you

 

[Shortround6]

I am a big fan of 6.5mm cartirdges and I have had two rifles built in 1990s for custom (at the time) 6.5mm cartridges.
1st was a 6.5mm X .308, an old wildcat from the 50s. Remington later introduced it as the .260 Remington.

.260 Remington - Wikipedia

en.wikipedia.org

And this may be larger than needed.

2nd was a 6.5rem benchrest. Basically the 6.5mm X .308 shortened from 51mm case length to 39.6mm length.

2nd is the 6.5 Swedish,
3rd is the 6.5 Carcano
4th is the .260 Remington.
6th is the 6.5 Grendel.

My 6.5 BR was pretty much a bit fatter Grendel, It easily fired a 120 grain bullet at 2600fps using a type of powder available in 1938-40. The sharper shoulder may have given feeding problems in an automatic weapon? I had a limited budget and needed to use a cartridge case that would fit an existing bolt face.
If you can accept the lower weight bullet and the lower impact the 6.5 will give the the same long range trajectory as the 7.5-8mm bullets and the same wind drift.

5th cartridge in the picture is the 6.5 Creedmoor which was pretty much developed because the .260 Remington with long boat tail bullets has the bullets sticking down into the powder space (down past the shoulder) and doesn't really have much more capacity than the slightly shorter Creedmoor.
But in WW II nobody was using extra pointy bullets with long boat tails. Short or medium boat tails yes but those require more steps or care in manufacturing of the accuracy goes to pot.

6.5 Swedish is/was a great cartridge but it was designed in the 1890s for the powder available at the time and for some reason it is just a little bit bigger at the back end than the German 7.9mm Mauser and the US .30-06 (and family) and so with the lack of cheap brass in the use it was not good choice for me. The difference in 500 or so pieces of brass about equaled the cost of custom chambering.

 

[yulzari]

FWIW, here is Gun Jesus, and hi's opinion about the 7.35x51 might surprise you

That would be my choice. A good fit for the task rather than 'let's see how big a bang we can squeeze in'.

 

[marathag]

My choice, as always, the Savage 250-3000, and it existed since 1915, based on the .30-06 case

It's a 2400 Joule class cartridge with 6 to 8 gram bullets at 8-900m/s

 

[yulzari]

Given the role of the weapon the ammunition will have to be carried by the section so big bangs mean heavy rounds. Lighter, with adequate bang, means more ammunition on hand and distributed amongst the riflemen. A factor often ignored by 'Top Trumps' posters.

The weapon is part of the firepower system available to the platoon commander and a choice of an OP weapon needs to take account of all the factors from ammunition production in the factories at the expense of something else down to how many bangs the user normally can have at his disposal as well as the ballistics. How many horses do you need to kill at 1,200 metres when normally you are shooting humans at no more than 600 metres and most often at 300?

The British conclusion in 1945 was that the Sten machine carbine was as valid a rifleman's weapon as the No4 Rifle in as much as, if the targets was out of Sten range, you had given him Bren Gun magazines and he passed them over to the Bren crew to do the longer shooting for him. Hence their search for a semi automatic rifle to combine with a section LMG using the same ammunition to simplify the whole arrangement.

Their original choice of a .270" intermediate for the Rifle No9 and Taden being remarkably similar to modern new rounds, albeit withstanding less pressures. I will admit that the 1944 intention was 7.92"Mauser for the SLEM/Bren pairing. The SLEM evolving into the FAL via FN49 over time.

Given what was around at the OP time the Carcano 7.35x51 seems a practical choice, whatever a technically superior one might have been. For Fallschirmjagers it would make sense to giver them Carcano 7.35x51 rifles to make their limited logistics even easier. You can squeeze more into the weapons air dropped containers too, which has to be a good thing.

 

[Timppa]

Cartridge is not so important in real world.
I let Gun Jesus decide between the real semi automatic rifles:

View: https://www.youtube.com/watch?v=Xp3h3CWmi1g&t=39s

 

[tomo pauk]

Cartridge is not so important in real world.
I let Gun Jesus decide between the real semi automatic rifles:

Cartridge is very important, as seen in the last 80 years.
Neither of these semi-automatics qualifies here, since the FG 42 was supposed to also do automatic fire while being hand-held. It was also almost half the weight of them.

 

[bf109xxl]

Cartridge is not so important in real world.

Undoubtedly, this profound thought is worthy of being put into my citation book.

 

[Shortround6]

Given the role of the weapon the ammunition will have to be carried by the section so big bangs mean heavy rounds. Lighter, with adequate bang, means more ammunition on hand and distributed amongst the riflemen. A factor often ignored by 'Top Trumps' posters.

The weapon is part of the firepower system available to the platoon commander and a choice of an OP weapon needs to take account of all the factors from ammunition production in the factories at the expense of something else down to how many bangs the user normally can have at his disposal as well as the ballistics. How many horses do you need to kill at 1,200 metres when normally you are shooting humans at no more than 600 metres and most often at 300?

The British conclusion in 1945 was that the Sten machine carbine was as valid a rifleman's weapon as the No4 Rifle in as much as, if the targets was out of Sten range, you had given him Bren Gun magazines and he passed them over to the Bren crew to do the longer shooting for him. Hence their search for a semi automatic rifle to combine with a section LMG using the same ammunition to simplify the whole arrangement.

Their original choice of a .270" intermediate for the Rifle No9 and Taden being remarkably similar to modern new rounds, albeit withstanding less pressures. I will admit that the 1944 intention was 7.92"Mauser for the SLEM/Bren pairing. The SLEM evolving into the FAL via FN49 over time.

Given what was around at the OP time the Carcano 7.35x51 seems a practical choice, whatever a technically superior one might have been. For Fallschirmjagers it would make sense to giver them Carcano 7.35x51 rifles to make their limited logistics even easier. You can squeeze more into the weapons air dropped containers too, which has to be a good thing.

These are some valid points.
It does somewhat depend on the priorities for the FG-42. As a squad weapon that is supported by a decent number of Belt fed 7.9mm guns (MG34/42) then the long range characteristics of the round used in the FG-42S (substitute) are of small importance and a slightly souped-up AK-47 round like the Carcano 7.35x51 will work fine.
Problem with the 7.35x51 is the light bullet for it's diameter which hurts down range ballistics. It was better than the round nose 6.5 Carcano but the Swedes, Japanese and others(?) had already figured out (and so did everybody using 7.62-8mm rifles) that using lighter pointy bullets at higher velocities worked better. They had also figured out by the end of WW I that boat tail bullets really changed things at long range.
The FG-42 doesn't seem to have been given a tripod but most armies figured that a bi-pod mounted gun was good for 600-800 meters.
IF (repeat IF) the Germans were looking for 600-800 meter fire from the FG-42 while waiting for the tripod mounted machine guns to arrive then a 6.5-7mm pointy bullet was probably the best way to go.
A gentleman I shot with in the 1970s and 80s had worked at Aberdeen proving grounds at the time the US was evaluating the British .280 cartridge vs the .308 and he was convinced the 7mm/.280 was superior to the .308 (7.62x51) in that you would get less recoil and have better ballistics from the lighter but more streamlined bullets. He made few rifles in custom 7mm cartridges. Now the real problem for experimenters like him and me was getting good quality bullets which tended to limit you caliber choices.
Basically (from memory) you could get a 150 grain 7mm bullet to do what a 168-173 grain .30 cal(7.62) bullet would do and a 130 grain 6.5mm bullet would do the same thing. Assuming fired at equal velocities.
The Soviets had used the 6.5 Japanese in the Fedorov Avtomat of 1917-1925 so the Germans must have been aware of it on some level.

However there is also the question of ammo manufacturing/supply and here many nations seemed to want to use as much existing tooling as possible.
German 7.9x33 Kurtz and the Soviet 7.62x39 and the US 7.62x51. The short rounds do not have the desired long range capability due to the short, blunt bullets but then they were supposed to have the belt fed machineguns for back up.

 

[bf109xxl]

Cartridge is very important, as seen in the last 80 years.

I don't know much about small arms development, but the books I've read stated that guns are designed for a particular cartridge, not the other way around. And adopting a new cartridge was always a much more complicated process than developing the weapon itself.
Sometimes it is possible to redesign a weapon to fit a cartridge with similar characteristics.

PS. The FG was a very expensive and technologically complex weapon. I'm not sure it was justified even for arming special forces with all its high performance.

 

[Shortround6]

I don't know much about small arms development, but the books I've read stated that guns are designed for a particular cartridge, not the other way around. And adopting a new cartridge was always a much more complicated process than developing the weapon itself.

In some cases it was to keep existing tooling/manufacturing capability. The cost of replacing the ammo factories or throwing out the older ammo may have exceeded the cost of tooling up for the new gun/s. Major countries sometimes had stockpiles of millions of rounds.

Production of US small arms ammo in WW II seems to be around 39-41 Billon rounds depending on source.

 

[tomo pauk]

I don't know much about small arms development, but the books I've read stated that guns are designed for a particular cartridge, not the other way around. And adopting a new cartridge was always a much more complicated process than developing the weapon itself.
Sometimes it is possible to redesign a weapon to fit a cartridge with similar characteristics.

Note that here the already established cartridges are in play, so there is little if any surprises for the guns' designer. He even receives caskets of ammo and dozens of barrels to speed up his work.
Also note that the premise of the thread is that the alternative FG 42 is developed from the ground-up around the non-German cartridge. IOW, there is no FG 42 that gets converted for another cartridge.

The FG was a very expensive and technologically complex weapon. I'm not sure it was justified even for arming special forces with all its high performance.

It was pretty much the ultralight Lewis gun. These don't come in cheap even as-is - even the British moved to the Bren in the 1930s, despite (because of?) the experiences with the Lewis gun production.
Designing the FG 42 around a less powerful cartridge might've put less strain on the designer to meet the 5 kg target. Perhaps even allowing it to fire from the closed bolt all the time, further simplifying the design.

Hmm - the German take on a very light BAR to became an alternative FG 42 might become a next topic a few months from now

 

[bf109xxl]

Are we considering purely design modification "for the sake of beauty" or are we still considering adoption? If the first, you could probably use almost any fully powered cartridge. But the era of intermediate cartridges was coming. For them, much simpler and cheaper weapons were created with close to FG 42 characteristics - ok, not quite the same, but acceptable. The combination of AK + RPD (then RPK) gave similar firepower to a platoon of paratroopers with more carried ammunition. Yes, FG was better, but from my point of view its complexity and price did not justify the difference in characteristics.

 

[Shortround6]

Cartridge is not so important in real world.

The real world can vary.
the vast majority of wars/battles since 1900 were fought with varying amounts of support machine guns and mortars/artillery which did leave the actual differences in cartridges rather insignificant.
However for the German paratroopers armed with 9mm pistols until they recovered their rifles and machine guns from supply containers having longer ranged weapons seemed rather desirable. The question is what the needed range.
US did fine with 5.56 in the jungles of SEA. Turned out to be not such a good idea in the deserts or mountains of the mid east. And the US had support weapons aplenty and radios all over the place. Changes in ammo helped and the US resorted to 7.62 machine guns in the squad/platoon to increase the small unit range.

The 7.92x33 makes a very fine short range (300 M?) round easily able to out range 9mm submachine guns. Problem comes in at longer ranges, say 300-600 meters. Forget the really long range stuff. The short blunt 7.9mm bullet slows down too fast. A 6.5-7mm bullet of identical weight (or close) of better shape and just a little more velocity can extend useful range by several hundred meters. And if you do not have a number of belt fed GPMGs that may be enough to keep things from going really bad.
However that is only a very percentage of combats out of the total so pick what you want/need/can afford.

 

[yulzari]

The Italians have all the kit to make Carcano 7.35x51 in quantity and have just decided to stick with the old 6.5mm instead of changing ammunition in an ongoing war. Ship it all off to Germany and build a factory around the outside. Job done.

Would the StG44 then be in 7.35x51 Carcano instead of 7.92x33? Not grossly disimilar in power even if the Kurtz is short and fat and Carcano long and skinny. Another saving on the production and logistics front.