>shaving down an LMG
LMGs were heavy and expensive.

>scaling up an SMG
SMGs were cheap, but heavy and inaccurate, and simple blowback isn't suited to handling rifle-powered cartridges.

>>65441351
LMGs were massive and overbuilt, which made producing them much more forgiving. Like by modern eyes, the BAR and Bren are just mag fed rifles, but they both weighed as much as an M240. That aside, both the French and Russians intended to mass issue semi autos; but the whole war thing got in the way.

>>65441351
It was unironically just inconvenient timing of economic conditions and wars starting/ending in the case of Britain and France, and I'm sure it played a decent part in the case of Russia/the USSR.
What I'm more surprised by is the relatively few number of self loading rifles that were based on preexisting bolt actions. You'd think it would be somewhat simple to design basically the same action but with a piston added to the top or side, but all the successful ones (or moderately successful at least) were built from the ground up and were hammer fired rather than recycling the striker mechanism of the preceding bolt guns.

Literally almost every single question of why some industrially produced item wasn't adopted earlier is most often
>Because it was really expensive and/or the tooling/metallurgy wasn't there yet

>>65441361
>Like by modern eyes, the BAR and Bren are just mag fed rifles
Please do not group together the BAR and Bren
The BAR is an automatic rifle
The Bren is an actual LMG

>>65441358
>>65441361
It is my understanding that much of the high weight of LMGs is due to heavy barrels and actions suitable for sustained automatic fire and aren't strictly necessary to create a functional rifle.
>and simple blowback isn't suited to handling rifle-powered cartridges
What was stopping them from using delayed blowback, something used successfully in a number of a assault rifles, as a minor modification?
I'm also under the impression that much of the inaccuracy of pistol caliber SMGs is due to them using pistol calibers in the first place.

>>65441405
>I'm also under the impression that much of the inaccuracy of pistol caliber SMGs is due to them using pistol calibers in the first place.
Why bother specifying pistol caliber when that is part of the definition of SMG

>>65441351
Too many men to have semi or full auto, supply lines and manufacturers wouldn't be able to keep up. They would have discouraged aiming too

>>65441405
>heavy barrels and actions suitable for sustained automatic fire and aren't strictly necessary to create a functional rifle
Yes, but people didn't yet know what parts were necessary and what could be cut out.

>What was stopping them from using delayed blowback, something used successfully in a number of a assault rifles, as a minor modification?
Delayed blowback isn't even close to a minor modification of simple blowback, it wasn't invented and/or wasn't considered for rifles.

>much of the inaccuracy of pistol caliber SMGs is due to them using pistol calibers in the first place
It comes from the relatively poor fit and finish of period SMGs (they were made to be dirt cheap and quick to produce) and the design of the SMGs themselves (open bolt, flimsy stocks, etc.). There's nothing inherently inaccurate about pistol ammunition.

>>65441410
>Too many men to have semi or full auto, supply lines and manufacturers wouldn't be able to keep up.
a laughably minor concern you have no idea what you're talking about, go look up artillery shell production

>>65441351
Same reason so many countries are still shit at drones right now, it's a rapidly changing field and governments want to wait and see which designs are best before committing to large scale procurement.
If you got 5 million SMGs during peace in 1930 sure you had SMGs but they were trash by 1940. Many refused to accept the inevitability of war with Germany until it was too late to run proper trails and procurement.

Today the analogue dropper drones running 2.4ghz ELRS of 2022 are already outdated and the drones of 2026 will be outdated by 2030. Everyone is hoping the "long peace" holds out long enough for the dust to settle and reveal the best drones for long term procurement.

>>65441418
Interwar, small arms ammunition was absolutely a problem. So was artillery shell production. You cannot look at wartime figures to dismiss peace time considerations. Lots of new muskets were turned down across the world in the 19th century specifically because of their higher rate of fire and the state’s worry that soldiers would blow through all their ammunition in three minutes. This kind of mentality was still present especially in peace time bean counters at the turn of the 20th century.

>>65441428
Yeah and they didn't have to scale up artillery production at all?

>>65441418
Individual heavy machine guns were pumping tens of thousands of rounds downrange per day when shit got hot. Every round going to a rifleman wasn't feeding the HMGs.
>>65441351
It would have been horrifically expensive to develop, produce, and issue the new rifle. Everyone had tooling and funding for the bolties. And on top of the other stuff Anons have mentioned, ammo still kind of sucked. Can you imaging sitting in a trench trying to keep an automatic-adapted Enfield running reliably on corrosive-primer spaghetti ammo made to "wartime standards" by Ishapore, in the middle of February?

>>65441432
They did, just as small arms production in general was scaled up and the ammo for it. But these decisions were five, ten year ones based on very strict and stringent government funding. Hell. The UK was still mothballing shipyards in 1938 to save a buck only to turn around and dump 5x the money they’d saved into restarting them. It may have been stupid. But it was also dumb.

>>65441449
>Individual heavy machine guns were pumping tens of thousands of rounds downrange per day when shit got hot. Every round going to a rifleman wasn't feeding the HMGs
Bizarre logic positing there was some hard wall of small arms ammunition production when it was a tiny part of overall logistics that could very easily be scaled up for something as materially trivial as semi-auto usage

>>65441351
Generals thought that giving the average soldier an automatic weapon would cause him to waste all his ammunition in the first ten seconds of combat.

>>65441498
The hard wall wasn’t actual production it was getting a government official to sign off on spending 0.003% more of the budget on doing so after you convince the generals and committee in charge of procurement that this is worth pursuing and to unlearn 60 years of small arms thinking. The British were heavily against issuing semi autos to their troops because they thought it would lead to wasted ammo and worse accuracy for instance. They had bolt action autism and that only really changed after they got their teeth kicked in repeatedly for three years by German small arms tactics.

>>65441351
>They had popular production rifle caliber LMGs before the first world war, everyone had been producing their own SMGs for decades before the second world war
>were there really no suitable candidates for such a conversion?
name your candidates then

>>65441457
>UK was still mothballing shipyards in 1938 to save a buck only to turn around and dump 5x the money they’d saved into restarting them
they had projected that Germany would only be capable of starting the war in the mid-40s. under those circumstances, it makes way more sense to concentrate your funds for the next 5 years or so on building actual ships, and shuttering underutilised capacity. they had to restart those dockyards because the war came sooner than expected.

why was it sooner than expected? because Germany's 1939 army was twice the size that Anglo-French military intelligence estimated, due to an array of techniques used to disguise buildup
furthermore, a key potential ally went over to the German side: STALIN, who turned down an Anglo-French-Russia treaty proposal, and signed the Molotov-Ribbentrop pact, essentially feeding Poland and France to the Nazis in order to buy time for the Red Army to retrain and rearm (Stalin had always expected to have to fight the Fascists)

not only did this free up Germany to concentrate wholly on the Allies without worrying about the USSR, it also meant securing hundreds of thousands of tons of petroleum and raw material imports to enable Germany's continued buildup

>>65441610
Like I said. May have been stupid, but it was also dumb. The British are almost solely to blame for both Stalin going over to the fascists in diplomatic talks and the war breaking out when it did for their moronic deal making, well really starting with isolating fascist Italy when they were the only ones actually standing up to Germany and making THEM go over to Hitler, and then just letting Germany remilitarize the Rhine and walk all over Czechoslovakia without a fuss. In general it seems like the UK government used time travel to make the absolute worst decision every time something came up. I know hindsight is 50/50 but man is basically everything Baldwin’s government did awful. Chamberlain was hardly any better, but I do have to at least give him the undue credit that he was handed an atrociously bad situation by the previous government’s antics. That he then played it as poorly as possible is a pox upon him sure but by 1937 the UK had already Kurt Cobain’d themselves on three separate occasions.

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>>65441596
Madsen MG, huot AR, browning AR, lahti-saloranta M/26 LMG, mendoza LMG, chauchat-ribeyrolles 1918 submachine gun.
I'll obviously leave out all the guns explicitly classified as automatic rifles prior to the end of the second world war.
>>65441408
Pic related uses a rifle cartridge but everything I find that references it refers to it as an SMG.
>>65441416
>Delayed blowback isn't even close to a minor modification of simple blowback, it wasn't invented and/or wasn't considered for rifles
Well it's definitely not that it wasn't invented, there were delayed blowback automatics going back to the first world war.

>>65441636
>Pic related uses a rifle cartridge but everything I find that references it refers to it as an SMG.
they can call it a chocolate sundae but it's not an SMG so don't be stupid

>>65441636
>Madsen MG
too complicated for both mass production and general use
>huot AR
Canadians were poor and the Brits too
>browning AR
prewar America was fiercely isolationist, viciously broken by the Great Depression, and essentially too poor (despite being the world's top economy) to bother about funding a land army, all available funds went to building a superb navy
>lahti-saloranta M/26 LMG
too complicated
>mendoza LMG
I'd have doubts about its accuracy, and it's chambered in Mauser making it no-go for any non-German nation
>chauchat-ribeyrolles 1918 submachine gun
frogs were even poorer then the bongs

>just simplify the design of these guns
"simplifying" to that extent would basically mean building a new gun

>>65441651
Firearm classifications are often arbitrary and have blurry lines.
Is an SMG not actually an SMG if it fires the rifle cartridge .22LR?
If an automatic is capable of firing a certain rifle cartridge and pistol cartridge without conversion would that make it a rifle or an SMG?
Is there even a definitional line at which a cartridge changes from a pistol cartridge to an intermediate cartridge?

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>>65441351

Money, the M1 Garand had the highest per-unit cost of any of the service rifles of the Second World War. And it likely only wound up so widespread because it was the adopted so early. The M1 was accepted into US service in 1936 and the changeover was already largely complete by the time of Pearl Harbor. If it had entered service in 1940 or 1941, it's likely that production would have been suspended or curtailed in favor of the already plentiful M1903.

>>65441358
>LMGs were heavy and expensive.
Uh, honey, no, the "L" in LMG stands for "light"

>>65441818
Pretty much every LMG made before the cold war weighed at least 20 pounds.

>>65441818
>Uh, honey, no, the "L" in LMG stands for "light"
and when talking about machine guns light means its not crew served

>>65441867
It's more about being in a fixed position (think big tripod etc) vs. being man-portable/on a bipod.

>>65441351
There aren't really self loading, you have to do that bit yourself. It's a bit of a misnomer, a con even

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>>65441351
A few different factors but as others mentioned LMGs used high powered rifle cartridges and making a light action that can shoot those safely is difficult with the manufacturing tech they had at the time.

Keep in mind that many WW1 machineguns used cast brass for complex parts, and everything else was machined.

By the end of WW2 metal stamping had been mastered and the Germans and the Americans had both tried intermediate cartridges successfully. With the technological developments they could finally make a battle rifle light enough to be practical.

The FAL has about as many cartridges of about the same power as the BAR, yet it's about half of it's weight.

>>65441351
>Be soviet union
>Make and assemble 750,000 svt-40s
>Pile them up on German border in purely coincidental military buildup pinkie promise nothing's going on
>Barbarossa happens first
>Lose all your semi automatic battle rifles in retreat
>Un-mothball m1891 tooling in the Urals need rifles NAO

Germany is a weird case where tactically they had a machine gun as the center of all infantry squads so were not lacking fire rate or suppression at all. While at the same time German autism had an incredibly hard time designing a semi automatic 8mm rifle. The Gweher-43 was a devhell nightmare.

>>65441404
Bren is also, an automatic rifle.

>>65442041
>Barbarossa happens first
More English provocation!

>The Gweher-43 was a devhell nightmare
do tell

>>65442041
>they had a machine gun...
>While at the same time they had an incredibly hard time designing a semi automatic 8mm rifle
The former informs the latter. They thought the machine gun was more important, so they focused on that first, then they had the idea to arm riflemen with an intermediate-caliber assault rifle, so they focused on that. The semi-auto full powered rifle was an afterthought to more important weapons.

>>65442050
Off memory so parts of this might be wrong
>2 different companies designing for same contract splitting resources and infighting to fuck each other over with a procurements department already barely interested in semi auto battle rifles
>Multiple long and short gas piston designs that failed or had fatal flaws
>Aforementioned captured svt-40s lead to the version eventually the "production" model having a gas cup recoil system design

>>65442050
NTA but
>hey this thing can’t shoot straight
>or cycle reliably
>these magazines are about as durable as wet cardboard
>I can’t hit SHIT this thing is actually worthless
>jams if it hasn’t been freshly oiled and still jams if it gets any dirt at all on it
>almost as heavy as an lmg
>also almost costs as much
>also it jams if you shoot it too much
>like not even very much you have to do a full clean and re-oiling of the system after like 100 rounds or it will start fouling and corroding the entire system and then it’s FUBAR mate

The first 6k made were so bad they just recalled and scrapped over a thousand of them, almost 2k because they just didn’t work. This specifically refers to the G41 version. The G43 was a refined improved version but by the time they had worked it out the STG44 was actually basically done and only didn’t get implemented because of Hitler autism. Oh also the G41 didn’t work in cold weather and in fact tended to rapidly self disassemble in freezing conditions if you tried to fire it. That said, there were some very good and reliable, well built ones that usually ended up being given to snipers actually. Build quality varied between German autism and the worst shit you’ve ever seen with seemingly no in between. But invariably every G41 was either directly recalled or invariably retired because the design just kind of sucked and was a mixture of overbuilt and under built which just resulted in the overbuilt parts breaking the underbuilt parts while being a pain in the ass to lug around.

>>65442078
>>65442108
thanks

Germans, they're so autistic they even make sure the fuckups are autistically, comprehensively fucked

>>65442110
G41 was effectively a prototype that they rushed to frontline duty which was itself heavily based on the SVT-40 which itself was effectively a prototype because Soviet industry sucked eggs. You can’t be too hard on it because between the two rival firms all but shooting at each other for the contract, the fact the contract was getting third rate materials because it was less of a priority than things like holy shit we need a tank gun that can actually go through T-34s were so fucked or oh my god Britain didn’t surrender we need so many more ships and why don’t any of our magnetic detonators work we’d have sunk half the British navy if these goddamned torpedos worked, and the fact it just did not get a lot of time to actually design things before blueprints hit the factory, well. There are worse guns that were made then. And now. I mean just look at India or the EBR.

>>65442078
To expand on why
>Gas cup recoil design
Was the final bad thing for the production 41 and 43 goes to as >>65442197 mentioned the svt-40 was also a weird piece of shit of a rifle and lifting elements of it's design for the G43 got it in service but like most interwar and early wartime designs they were some or the worst engineering choices. The gas piston setup buried in the guts of both the svt38/40 and g41/43 would get absolutely fucked by corrosion from the ammo and fowling buildup. The svt40 also had frame stretching issues the more rounds went through the gun which with the tilting bolt means they just would stop working and it's effectively unrepairable.

Both the johnson rifle and M1 aren't free of weird firearm design either. Pretty much every tested and service battle rifle of WWII was weird or borderline broken.

>>65441498
The wall isn't specifically small arms ammo production. It's *good-quality* ammo. HMGs of the era were fucking mules. Bolt-action guns don't care. But a gas-operated conversion gun sure as fuck does. Blowing corrosive primer salts up into the gas port and tube is going to clog it up, weaken everything, and eventually blow up the gun one way or another.
Any conversion or replacement would have to issue millions of rifles in a matter of a couple of years. The British were still manufacturing and issuing fucking Martinis to backline troops and cadets because they literally could not afford to drop Enfield production for frontline troops. Establishing multiple new factories with higher tolerances and more machining steps/components, training new workers, and ensuring a steady supply of ammo high-quality enough to feed them while keeping the existing troops armed was unacceptable to all of the powers involved. Especially when several of them were already buying a significant chunk of their guns from neutrals because they couldn't afford to equip their own with the existing factories

>>65443108
>The British were still manufacturing and issuing fucking Martinis to backline troops and cadets because they literally could not afford to drop Enfield production for frontline troops
Complete bullshit

>>65441404
Semantics.

>>65442063
>They thought the machine gun was more important
It was

>>65441351
the simple, boring answer is that while rifles are highly visible because so many people use them, they aren't a very high priority for military planners compared to really expensive projects like tanks, ships and airplanes and improved artillery, that make much more of a difference on the battlefield. Also, basically the entire world was poor as shit due to the great depression, and prior to that there was a ten to fifteen year period where nobody wanted to invest in defense because they had a hangover from World War 1.

>>65441396
I think you would need to make so many changes to the design to include a gas system that it's easier to start from the ground up.

>>65441416
>Delayed blowback isn't even close to a minor modification of simple blowback, it wasn't invented and/or wasn't considered for rifles.
delayed blowback was pretty specifically invented for rifles, not pistol caliber weapons. the most popular delayed blowback SMG was derived from a full sized rifle.