3.5lb carbine requirement instead of 5lb?

[tomo pauk]

M1 carbine was at 5.5 with an empty 15rd mag and without sling (requirement was 5lb, so no biggie), and a bit above 6 lbs with sling and ammo, with 300 yds effective range.
For the sake of discussion, let's say that US Army's requirement is different this time. It calls for an even lighter weapon (3.5lb without ammo and sling, 4 lb with ammo and sling) , with effective range comparable with the Thompson SMG, ie. 150 yards. Extra merit points can be earned if the 'light carbine' has the effective range of 200 yds. Note that low specified weight and relatively long range will most likely exclude the simple blowback weapons. Semi-automatic fire. A 15 rd detachable magazine is required.
Ammo choice - anything that can be designed and manufactured by the ammo technology of the day. Use the existing cartridge (home grown or foreign), or a suitably modified existing cartridge, or something new. Bullet of the chosen ammo type, when fired from carbine, needs to be able to incapacitate an enemy soldier up to at least 150 yds.

(specs for the M1/2/3 Carbine are attached)

 

[marathag]

Losing the wood furniture(and kit stored inside the stock) for magnesium castings with Bakelite pads and wire stock, you might get there.
The Iverson Johnson Enforcer Pistol, with 10" barrel and walnut pistolgrip and full length walnut handguard was 4lbs.

 

[Blue cat]

M1 carbine was at 5.5 with an empty 15rd mag and without sling (requirement was 5lb, so no biggie), and a bit above 6 lbs with sling and ammo, with 300 yds effective range.
For the sake of discussion, let's say that US Army's requirement is different this time. It calls for an even lighter weapon (3.5lb without ammo and sling, 4 lb with ammo and sling) , with effective range comparable with the Thompson SMG, ie. 150 yards. Extra merit points can be earned if the 'light carbine' has the effective range of 200 yds. Note that low specified weight and relatively long range will most likely exclude the simple blowback weapons. Semi-automatic fire. A 15 rd detachable magazine is required.
Ammo choice - anything that can be designed and manufactured by the ammo technology of the day. Use the existing cartridge (home grown or foreign), or a suitably modified existing cartridge, or something new. Bullet of the chosen ammo type, when fired from carbine, needs to be able to incapacitate an enemy soldier up to at least 150 yds.

(specs for the M1/2/3 Carbine are attached)
View attachment 792799

Maybe something based on an existing semi auto pistol with a basic skeleton stock and somewhat longer barrel ? Maybe a 1911 chambered for a hot 9 or 10mm cartridge could be a starting point ?

A quick web search seems to turn up 10mm rounds fired from carbines that have under 20 inches of gravity drop at 150 yards. I will let others delve into how much retained energy is required at long range. Perhaps with a dual aperture sight 20 inches of gravity drop would be manageable ? That being said if a Thompson in .45 was considered effective to 150 yards I suspect a 10mm carbine (with a cartridge with an overall length that works in a 1911) would be as well.


Edit to add, if needed perhaps 1911 internals used for a carbine in the 1930’s would / could likely be beefed up a bit to cope with any long term reliability / durability issues caused by rounds similar to todays full power 10mm rounds ?

 

[Driftless]

Rube question: is there a weight difference for gas-operating gear vs blowback hardware? Is there enough difference there to affect the choice of cartridge as well?

 

[marathag]

Rube question: is there a weight difference for gas-operating gear vs blowback hardware? Is there enough difference there to affect the choice of cartridge as well?

Blowback for anything more powerful than 380 is likely to be heavier than a locking system.
Blowback is just cheap and easy, not better from most other categories

 

[tomo pauk]

Maybe something based on an existing semi auto pistol with a basic skeleton stock and somewhat longer barrel ? Maybe a 1911 chambered for a hot 9 or 10mm cartridge could be a starting point ?

A quick web search seems to turn up 10mm rounds fired from carbines with that have 20 inches of gravity drop at 150 yards.

Hmm - a rimless 357 Magnum with a 'normal' ball projectile? Same, but necked down to .30? A hotter .38 Super, or a version of it? The 1911's versions were already chambered for that cartridge.

Losing the wood furniture(and kit stored inside the stock) for magnesium castings with Bakelite pads and wire stock, you might get there.
The Iverson Johnson Enforcer Pistol, with 10" barrel and walnut pistolgrip and full length walnut handguard was 4lbs.

I'd certainly look to get rid of the wooden furniture as much as possible. The Automag III pistol was even lighter, under 3 lb; granted, not everyone was with hands big enough to comfortably hold that pistol's grip.
Can we expect from an average GI to hit a man-sized target at 150-200 yds without the shoulder stock?

 

[marathag]

Hmm - a rimless 357 Magnum with a 'normal' ball projectile? Same, but necked down to .30? A hotter .38 Super, or a version of it? The 1911's versions were already chambered for that cartridge.


I'd certainly look to get rid of the wooden furniture as much as possible. The Automag III pistol was even lighter, under 3 lb; granted, not everyone was with hands big enough to comfortably hold that pistol's grip.
Can we expect from an average GI to hit a man-sized target at 150-200 yds without the shoulder stock?

Anything longer than 357 gets to be a thick grip.
I have gorilla hand, so never a a real problem for me, but I can see why thing like that KalTec in 22 Magnum is a literal handful, let alone the longer 45 Magnum or 44 Automag

 

[tomo pauk]

Anything longer than 357 gets to be a thick grip.

It is probably so.
.30 Carbine was longer than the 7.62 Tokarev by ~5.5mm. We'd probably want to beat slightly the 7.62 Tokarev, when it is about viability to reach out to 150 m and beyond? The .357 Magnum when fired from rifle at 1550 fps still has over 1000 fps at 250 m (!), despite the hollow point bullet per this calculator. Drop is under 20 in at 200 yds. All in all it looks very usable to me.
Neck it down to .30 and it is even better beyond 100 yds, with lower recoil, just keep the case length at 30mm so it is not too long. Similar treatment can be applied to the .38 Super.
Granted, the OTL .30 Carbine can lose these 3mm too by 'moving' the shoulder close to the base and cutting off the 3mm, too, and still very much qualify.

 

[tomo pauk]

For some reasons, the quote function is not working for me.

I am thinking something smaller than .45 likely makes sense (likely larger magazine capacity for a given length magazine, probably better long range ballistics, and would allow for a “hotter“ round suitable for a beefed up (if needed) action in a carbine that could not be fired (or at least not easily fired with anything like full performance ? in existing .45 cal firearms.)

We're in agreement here.
A reason why I've mentioned the .38 Super is that it was working in the 1911s, and these 1911s were carrying two rounds more than the .45 versions. Seems like the .38 Super was popular in guns' competitions well after it was introduced. It was also more powerful than the 9x19.

 

[Blue cat]

For some reasons, the quote function is not working for me.



We're in agreement here.
A reason why I've mentioned the .38 Super is that it was working in the 1911s, and these 1911s were carrying two rounds more than the .45 versions. Seems like the .38 Super was popular in guns' competitions well after it was introduced. It was also more powerful than the 9x19.

Yeah and just to add, trying to chamber and or fire ammunition other than the caliber and type a fire arm is / was designed to accept is not something people should do.

 

[marathag]

It is probably so.
.30 Carbine was longer than the 7.62 Tokarev by ~5.5mm. We'd probably want to beat slightly the 7.62 Tokarev, when it is about viability to reach out to 150 m and beyond? The .357 Magnum when fired from rifle at 1550 fps still has over 1000 fps at 250 m (!), despite the hollow point bullet per this calculator. Drop is under 20 in at 200 yds. All in all it looks very usable to me.
Neck it down to .30 and it is even better beyond 100 yds, with lower recoil, just keep the case length at 30mm so it is not too long. Similar treatment can be applied to the .38 Super.
Granted, the OTL .30 Carbine can lose these 3mm too by 'moving' the shoulder close to the base and cutting off the 3mm, too, and still very much qualify.

The .30 Carbine is just a slightly tapered .32 WSL that's a mm longer.
It could be shorter, it didn't use all that case capacity as it was

 

[marathag]

A reason why I've mentioned the .38 Super is that it was working in the 1911s, and these 1911s were carrying two rounds more than the .45 versions. Seems like the .38 Super was popular in guns' competitions well after it was introduced. It was also more powerful than the 9x19.

Was also popular with LEOs and the Motor Bandits in the early '30s, as the .38 Super could penetrate automobile bodywork better that the common .38 Special or 45ACP could, besides a flatter trajectory that aided accuracy at range

 

[Ravinoff]

Ever see a Lebman or Swartz 1911 conversion? John Dillinger fairly famously used one, a full-auto conversion by Hyman Lebman with a Thompson foregrip and Cutts compensator. In .38 Super, too, most of the auto conversions were as far as I can gather. So I'd imagine something like this. Standard .45 Auto, .38 Super or if you need a bit more punch, .45 Remington-Thompson (.45ACP with the case extended by about 1/8"), which is close to the mostly-forgotten .45 Winchester Mag. That is, if you're doing something pistol-based. More or less an American Artillery Luger or C96 without the Teutonic complexity.

For something more conventionally rifle-like? A Mr. Russell Turner of Pennsylvania submitted the below for the Light Rifle trials that became the M1 Carbine. It did poorly even after some reworking and a more traditional stock. Came in at 4.5lbs with a 5-round mag and sling, but I think you could bring that down a bit with some reshaping of the receiver and bolt.

If I might comment on the general idea though, with 1940 tech/materials and (more importantly) Ordnance officers, I don't think 3.5lbs is a plausible goal. That's not an easy mark to reach today even, not without Kel-Tec levels of polymer everything or majorly skeletonizing every possible component. And consider too that M1 Carbines were sort of a secondary production item made by a massive list of companies not experienced in making firearms. The design needs to be simple, rugged and easy to make with existing equipment. Rock-Ola Jukebox Company or IBM aren't going to have the necessary setups to work with casting magnesium.

 

[Orcbuster]

So am I going to be the only one to ask why the limit would be set at 3.5 lbs?

I know the OP says for sake of discussion but the why is what makes such a discussion interesting in the first place.

 

[marathag]

Rock-Ola Jukebox Company or IBM aren't going to have the necessary setups to work with casting magnesium.

Magnesium casting picked up very quickly, thanks to what Dow Chemical had done just before the war, with research to drop the price while allow to make casting easier.
In 1938, Dow, the sole producer at this time, produced around 2500 tons. After Henry J Kaiser's new Magnesium plant in California tripled that at first, and increased. was running in 1941, was just the start. 15 plants across the Nation were in operation in 1943, 291,000 tons per year.

 

[marathag]

For something more conventionally rifle-like? A Mr. Russell Turner of Pennsylvania submitted the below for the Light Rifle trials that became the M1 Carbine. It did poorly even after some reworking and a more traditional stock. Came in at 4.5lbs with a 5-round mag and sling, but I think you could bring that down a bit with some reshaping of the receiver and bolt.

Cut the barrel length down to SMG length(11-12") and pull out wire stock like the M3, 3.5 pounds is easy in reach

 

[Ravinoff]

Magnesium casting picked up very quickly, thanks to what Dow Chemical had done just before the war, with research to drop the price while allow to make casting easier.
In 1938, Dow, the sole producer at this time, produced around 2500 tons. After Henry J Kaiser's new Magnesium plant in California tripled that at first, and increased. was running in 1941, was just the start. 15 plants across the Nation were in operation in 1943, 291,000 tons per year.

Actually, that brings up a better question, was the technology for casting magnesium at the time even consistent enough for use in guns? A quick poke around on Google tells me there are a couple companies out there making gun parts in magnesium alloys, but only one using an actual high-purity Mg blend (and that's for a chassis stock, so definitely machined after casting). The rest is mostly Zamak or 7068 aluminum, which is only about 2.5-3% magnesium. And looking anecdotally at some forum comments, die-casting parts doesn't have a great reputation. Aluminum is war essential elsewhere, so it's not likely you'll be using anything in that family.

Now before someone gets going on me about metallurgy, that's specifically talking die-cast parts, not castings in general. Ruger fairly famously uses investment-cast steel in their nigh-indestructible revolvers, and sand-cast magnesium is common in aerospace parts. Die-cast just tends to have problems with bubbles and other defects.

 

[tomo pauk]

So am I going to be the only one to ask why the limit would be set at 3.5 lbs?

I know the OP says for sake of discussion but the why is what makes such a discussion interesting in the first place.

The M1 Carbine was a result of request for a weapon much better than the 1911 pistol the non-combat servicemen were carrying, while being 'half as much as the Thompson SMG'; at least this is how Wikipedia says it. As a replacement for a pistol, going to 3.5lb (4 with ammo and sling) means the weight increase is not that great, so these servicemen can lug the weapon all day while serving their 155mm or 105mm gun, or while driving, or while operating a radio station.

 

[brookso]

M1 carbine was at 5.5 with an empty 15rd mag and without sling (requirement was 5lb, so no biggie), and a bit above 6 lbs with sling and ammo, with 300 yds effective range.
For the sake of discussion, let's say that US Army's requirement is different this time. It calls for an even lighter weapon (3.5lb without ammo and sling, 4 lb with ammo and sling) , with effective range comparable with the Thompson SMG, ie. 150 yards. Extra merit points can be earned if the 'light carbine' has the effective range of 200 yds. Note that low specified weight and relatively long range will most likely exclude the simple blowback weapons. Semi-automatic fire. A 15 rd detachable magazine is required.
Ammo choice - anything that can be designed and manufactured by the ammo technology of the day. Use the existing cartridge (home grown or foreign), or a suitably modified existing cartridge, or something new. Bullet of the chosen ammo type, when fired from carbine, needs to be able to incapacitate an enemy soldier up to at least 150 yds.

(specs for the M1/2/3 Carbine are attached)
View attachment 792799

Losing the wood furniture(and kit stored inside the stock) for magnesium castings with Bakelite pads and wire stock, you might get there.
The Iverson Johnson Enforcer Pistol, with 10" barrel and walnut pistolgrip and full length walnut handguard was 4lbs.


Actually, that brings up a better question, was the technology for casting magnesium at the time even consistent enough for use in guns? A quick poke around on Google tells me there are a couple companies out there making gun parts in magnesium alloys, but only one using an actual high-purity Mg blend (and that's for a chassis stock, so definitely machined after casting, ar 15 handguard( https://gritrsports.com/shooting/accessories/handguards/ ) would need to be machined as well most likely). The rest is mostly Zamak or 7068 aluminum, which is only about 2.5-3% magnesium. And looking anecdotally at some forum comments, die-casting parts doesn't have a great reputation. Aluminum is war essential elsewhere, so it's not likely you'll be using anything in that family.

Magnesium castings might be the solution, however it would require machining afterwards for sure. 3.5 lbs ammoless and slingless sounds pretty low, but not impossible.

 

[tomo pauk]

Magnesium castings might be the solution, however it would require machining afterwards for sure. 3.5 lbs ammoless and slingless sounds pretty low, but not impossible.

Steel stampings here, aluminium alloy there, bakelite pistol grip and hand grip? Barrel length can be about 10 inch, as on the SMGs of the day, again less weight than the long barrel used on the M1 Carbine.
I'd certainly prefer layout of an Uzi, or a (stocked) pistol to keep the weight down - in other words, magazine goes in the pistol grip, behind the trigger.
The wire buttstock like used on the Grease Gun should improve the hit probabilities beyond 100 yds, while not being too heavy.

@cortz#9 - can you whip up something here