Straight-blowback carbine in .30 Carbine?

[cluttonfred]

The .30 Carbine round was developed from the .32 WSL (Winchester Self-Loading) cartridge used in the straight-blowback, semi-automatic Winchester Model 1905 rifle. The family of Winchester Self-Loading cartridges and straight-blowback rifles also included .35 WSL (Model 1905), .351 WSL (Model 1907) and .401 WSL (Model 1910). In power, the .30 Carbine is right in the middle of this group of five cartridges at 710/779/967/1400/2037 ft-lb, respectively.

The wood-and-steel Model 1905 in .32 WSL or .35 WSL was pretty handy at under 8 lb with a 22 in barrrel. I would think that a modern, straight-blowback carbine in .30 carbine with a 16" barrel, 10-round magazine and lightweight synthetic stock could be kept to around 7 lb, or about the same as a Ruger Mini-14. With such a simple action it would be cheaper and simpler than the Mini-14 or the original M1 Carbine. And it wouldn't have to be much more expensive than a Hi Point pistol-caliber carbine, though hopefully it would be a lot better looking. ;-)

Would there any interest in a straight-blowback carbine in .30 Carbine, perhaps styled like the original Winchesters?

 

[briansmithwins]

Simple blowback action is going to require a pretty massive bolt to keep the breech from opening too fast and either tearing the head off or having the case blow out.

Chinn's The Machine Gun Vol. 1 has the equations for calculating the bolt weight that's required for blowback operation.

BSW

 

[Tirod]

Would there be any profit potential for it? Tooling up to make said carbine would involve investing money and a minimum number would need to sell to break even after 5 years.

Winchester couldn't compete in this market, but at three times the price the Japanese seem to keep up. The "ReMarlington" isn't necessarily doing that well as the parent corporation is deep in debt.

The demographic that treasures traditional guns is moving upscale in spending and getting older, too. The newer shooters aren't interested, they are buying AR's.

The dissolution of traditional families is killing off traditional guns. The experience of shooting early in life has moved to games that feature modern issue weapons.

Gauging market demand to see a profit is the witchcraft of marketing, sometimes you win, odds are in ten years 87% fail. It takes a venture capitalist with some naivete to finance it. A traditional gun in an obsolete cartridge that doesn't rate highly for hunting or self defense already has strikes against it.

 

[Jim Watson]

Why would I buy a 7 lb blowback when I can have a 5.5 lb gas op? Why would I buy a .30 carbine when I can have a way kewl .300 BO?
I don't know if cheap will sell.

I think the .30 carbine runs at higher pressure than the WSL series and would be tough to balance a blowback for.

The Cristobal Carbine is a delayed blowback designed for a banana republic. It might fit your spec.
http://www.guns.com/2014/01/14/cristobal-carbines-made-d-r/

 

[Ash]

Tirod, I disagree that the 30 carbine is a bad self-defense round. A 30 carbine makes a better self-defense firearm than a 9mm and equivalent to the .357 carbine. It is neither ineffective nor obsolete it its designed role.

I think the problem lies more in your other observation about firearms encountered in games. Traditional guns lack panache and don't look like an AR. You cannot easily festoon them with rails, lasers, lights, red dots, or a can opener. Looks to many are more important than performance, and that's the way it goes. I can empathize, because when I was just out of college during the Clinton years, I Tapco'd out my first SKS. I learned my lesson quickly and discovered the simplicity and ease of carry found with a smooth wooden stock and no extra extensions or encumbering parts. I don't have to look like Call of Duty Modern Warfare at the range or at home. I don't mind those who do and they are the ones who drive the market at present.

I see it as an uphill battle, but then, there are modern-made M1 Carbines so that may not necessarily be impossible. I imagine were Hi Point to come out with a 30 carbine, many here would begin to crow about it.

 

[USAF_Vet]

I mentioned a Winchester 1905 .35WSL in another thread, with consideration to buying the old girl and modernizing it with a new, more common cartridge. There's a used (obviously) rifle on the rack at my LGS and I considered the possibility of rechambering it, but as with most pipe dreams, it died in the pre-development phase. Glad to see I'm not the only guy here who sees some viability in these old designs, if for nothing but nostalgia. I do still see a very tiny niche for guns like the Winchester 1905 and the Remington model 8/81.

.30 carbine is a much much hotter round than the old Winchester Self Loading cartridges, and that alone reduces its viability in a straight blow back. If a conversion of these old guns were to be done, it would have to be a modern, common cartridge with similar pressures to the original cartridge. .380 ACP or .32 ACP might be a good substitute, maybe even 9mm if you were to beef up the bolt to delay the blow back. It works for the Hi Point carbines all the way up to .45 ACP.

I don't see any company tooling up to remake these old designs with a modern twist, for the same reasons great guns like the Marlin Camp 9 and Ruger police carbines died off. Modern pistol caliber and intermediate carbines are plentiful. You've either got the Hi Point, as a functional, low budget carbine, the Kel-Tec which is generally considered vaporware, and the higher end PCCs which cost as much as an AR or AK.

I love the idea, but these would have to be one-off creations.

 

[Justin]

The only reason to build a straight blowback gun is because they're easy to design and cheap to produce.

I see no point in producing a cheap gun chambered for an expensive cartridge like .30 Carbine.

On top of that, as already stated, the people who are interested in buying a short-range 30 caliber cartridge are all buying ARs chambered in 300 BLK, with .30 Carbine being relegated to people who are interested in WWII history or the occasional deer hunter.

 

[barnbwt]

"The only reason to build a straight blowback gun is because they're easy to design and cheap to produce."
And easiest to build --it's not like the store is the only place to get what you want.

TCB

 

[briansmithwins]

The only reason to build a straight blowback gun is because they're easy to design and cheap to produce.

If you're making a million of them. Making just one it isn't going to be that much simpler to either design or produce.

BSW

 

[cluttonfred]

Thanks, all, for the comments. This is just a concept, of course, as I don't have a gun factory at my beck and call, but I was thinking about this as a commercial venture rather than a one-off project, hence the straight-blowback operation.

On the caliber question, personally I think that .30 Carbine a cartridge that deserves a second look as about the perfect home defense or police patrol long gun caliber--just enough gun and not too much right out to about 100 yards. YMMV, of course.

On Justin's points about cost and caliber, as of five minutes ago at ammoseek.com, the price per round for the absolute cheapest remanufactured .300 BLK rounds was 46¢, moving up to 64¢ for new, name brand Fiocchi ammo. For comparison, the absolute cheapest .30 Carbine out there is steel-cased Tula at 28¢, moving up to 34¢ for new steel-cased Armscor and 38¢ fpr Prvi Partizan.

Not only is .30 Carbine much cheaper than .30 BLK, but when you run the numbers, it's actually cheaper than or equal to 7.62x39mm or .223 in brass cases, though slightly more expensive in steel case.

 

[Swampman]

40,000 PSI is fairly high pressure for a straight blowback.
Bolt weight would have to be high and even with a heavy bolt, it'd probably be hard on brass.

Neither Hi Point nor other manufacturers have brought out blowback pistol caliber carbines in .357 SIG, even though the bolt face is identical to that of the 40 S&W and the barrel to 9mm, which at first glance, should make the conversion simple and inexpensive.

I think one of the main reasons it hasn't been done is because like .30 Carbine, the .357 SIG operates at 40,000 PSI, considerably hotter than the pistol rounds currently used.

 

[briansmithwins]

40,000 PSI is fairly high pressure for a straight blowback.

9mmP NATO runs at 36,500, which isn't that far off from .30 carbine.
http://en.wikipedia.org/wiki/9×19mm_Parabellum#9_mm_NATO_standard

BSW

 

[Swampman]

9mmP NATO runs at 36,500, which isn't that far off from .30 carbine.

So?

9mm +P is rated at 38,500 PSI, that's even closer.

But everything has a cut off point.

Show me a list of current production, straight blowback weapons that use cartridges running at 40,000 PSI or more.

They may be out there, but I'm unaware of them.

 

[Sunray]

"...I don't know if cheap will sell..." Look at the assorted Kel-tecs. Not cheap price wise though.
"...carbine in .30 Carbine..." Ammo has gotten too expensive. Starts at about $25 per 50vs about $12 for 9mm. The days of cheap milsurp ammo are long gone.

 

[kBob]

Winchester designed SLRs of the 1900's as blow backs (get a load of their internals some time) but when they designed the M-1 carbine they went with gas operation with a locked bolt.......hmmm that indicates something.

Of course they could not have made weight for the US Army competition and contracts with a blow back.

As for folks building guns other than the M-1 carbine in .30 carbine..... let's see.

Kimbal auto pistol, I think went under in one year.....when ammo was cheap.

Marlin Levermatic, I think they offered it two years in .30carbine.

Auto Mag Some number, ever actually seen one?

and the most successful I am aware of is the Ruger Blackhawk single action revolver.....and those have not sold like hot cakes.

Oh yeah and I handled an Olympic Arms prototype for an AR 15 based .30 carbine I have never heard of since.

The cartridge is basically a one trick pony.....it runs M-1 carbines well.

-kBob

 

[Ohio Gun Guy]

There was a lot of designing done in the 20's-30s-40s to come up with reliable self loading Rifles (Rounds with higher pressure). There are a few branches of development, but successful designs offer some version of delayed blow back or gas operating system.

Fluted chambers, lubricated rounds, etc were all tried....


I doubt you'll see many (If any) pure blow-back rifles at least not for any high pressure rounds.

 

[briansmithwins]

So?

9mm +P is rated at 38,500 PSI, that's even closer.

But everything has a cut off point.

Show me a list of current production, straight blowback weapons that use cartridges running at 40,000 PSI or more.

They may be out there, but I'm unaware of them.

The aforementioned 5.7mm runs at 50kpsi and is available in the P90, which is a simple blowback operated gun.

BSW

 

[351 WINCHESTER]

The .351 as loaded by Winchester and Remington was right at 40,000 psi. I have seen .30 carbine conversions to the 07 and even the 05 self loaders. I just don't see the reasoning as it's expensive and for little "gain".

 

[justin22885]

well for those of you wondering how the cartridge pressure and capacity and bullet weights will effect the design, its safe to say a bolt of around 3.2-3.25lbs would be sufficient for a .30 carbine.. straight blowbacks tend to be more sensitive for bullet weight, so while a .30 carbine may need 3.2lbs, the .22 spitfire which is the 30 carbine necked down to a .22 caliber with a 40-50 grain projectile would only need a bolt mass weighing 1.4-1.5lbs

so if you were to create a direct blowback SMG/carbine using .22 spitfire / 5.7mm johnson, which is 30 carbine necked down to a 22 and used 40 grain .224" projectiles, your final product would weigh no more than an M1 carbine, be about 1000 times simpler to produce, be more accurate, and with this cartridge would give you a PDW with ballistics superior to 5.7x28mm and closer to that of the really short 5.56 barreled rifles

 

[justin22885]

for those of you wanting to know, theres an easy formula to calculate bolt weights.. its basically 0.0000109 x bullet weight in grains x bullet velocity in FPS and thatll get you into the ballpark of what youd need.. information here http://orions-hammer.com/blowback/

 

[barnbwt]

There's a little more to it than just bullet weight (doesn't take tapered cases into account, which put the exact same bolt thrust on the unsecured bolt body, but don't necessarily generate the same momentum by way of increased velocity) but Orion's stuff is a good starting point. Good because his numbers are all incredibly high above the minimum of what is safe to use (i.e. a good starting place for debugging)

High pressure blowbacks require thick case heads and friction reducing measures (coatings or chamber flutes) to prevent tearing of cases or blow out, and are still really rough on precious brass. The PS90 and five-seven are both rather hard on cases (which hang together mostly because the brass is so thick)

TCB

 

[justin22885]

as i said, puts it in the ballpark, but i agree that there would be other problems involved as youve said, higher pressure meaning most brass at higher pressures probably isnt going to be able to handle the extraction process very well, so thats an additional challenge that would have to be overcome.. chamber polishing, dual or an extra large extractor to increase surface area of contact, stuff like that may work but ultimately it would probably come down to trial and error to dial it in just right

however, 30 carbine is what? 38,000 PSI?.. only a couple K higher than 9mm, so its doubtful you would need to go through any great length to deal with added pressure, conventional blowback shouldnt be too hard on it, its just for the 30 carbine youre going to need a bolt over 3 pounds

 

[cluttonfred]

Thanks, guys, some great feedback and resources there. From Justin's link...

Cartridge .30 Carbine
Bolt weight 3.2 pounds
Bolt thrust 4.0 kpounds
Bullet 100 grains
Velocity 2200 fps
Caliber 0.308 inches
Base 0.356 inches
Proof 52.0 kpsi

Since standard .30 Carbine ball is actually 110 grain at about 1990 fps, applying the same formula results in almost no change to the predicted bolt weight at 3.19 lbs.

So it's clear that a straight blowback .30 Carbine is going to require a hefty bolt (more than half the weight of an unloaded gas-operated M1 Carbine). That might be OK for a home defense and police patrol carbine that will not be carried much if the mechanical simplicity helped bring the cost down. The weight would also further reduce the already very mild .30 Carbine recoil.

Still, it's probably also woth looking at delayed blowback (H&K/CETME roller, Kiraly-Cristóbal/FAMAS lever, etc.) or even short-recoil (perhaps with the barrel pivoting down Browning-style like a big automatic pistol) options to see if any of those would bring the weight down substantially without introducing too much complexity.

Wheels are turning....

Cheers,

Matthew

 

[Swampman]

@ briansmithwins
I stand corrected sir, and you do! (Win I mean )

 

[Bexar]

for those of you wanting to know, theres an easy formula to calculate bolt weights.. its basically 0.0000109 x bullet weight in grains x bullet velocity in FPS and thatll get you into the ballpark of what youd need.. information here http://orions-hammer.com/blowback/

Justin...Thanks for that link. I've always been fascinated by firearms design and theory. More good reading and TI-89 numbers crunching for me. Yay!