Bit of a thought experiment for you all

fightinghamster

fightinghamster

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Was hanging with the bys today talking nonsense as one does and I had a thought, since 300 black out is just .223 necked up to .30 caliber. And 5.7x28 is essentially mini .223 (the bullet diameters are even the same), what’s to stop some enterprising young lads from necking up 5.7x28 to .30 caliber (probably using 30-30 or 7.62tok bullets) and having a 30 blackout, 28 fury? We’ll workshop the name, outside diameter of 5.7x28 is .311 so a .309 bullet should fit no problem, I don’t have the machine tools necessary to experiment with this, but it’s a nice thought, anyone care to weigh in? Has this been done and failed? Never been done? Feel free to chime in
 
300 BLK is not 223 necked up.

300 BLK is 221 Fireball necked up, which makes it 7.62x35.

Necking up 5.7x28 would give you 7.62x28. It'd be shorter and less powerful than 300 BLK and there would be no point and no benefit. It would also be a problem in 223 length magazines. The entire point of 300 BLK is that it will fit in and feed reliably from 223 length magazines.

It hasn't been done because it makes no sense.
 
I Dont Care About You said:
300 BLK is not 223 necked up.

300 BLK is 221 Fireball necked up, which makes it 7.62x35.

Necking up 5.7x28 would give you 7.62x28. It'd be shorter and less powerful than 300 BLK and there would be no point and no benefit. It would also be a problem in 223 length magazines. The entire point of 300 BLK is that it will fit in and feed reliably from 223 length magazines.

It hasn't been done because it makes no sense.
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I’m not saying to use it in 223 mags, that makes no sense, 300 BLK is used in 223 mags I’m saying use it in 5.7x28 mags, a straight wall .30 caliber cartridge that can be used in something like a p90 mag, I’m picturing the performance to be similar to 30 carbine
 
fightinghamster said:
I’m not saying to use it in 223 mags, that makes no sense, 300 BLK is used in 223 mags I’m saying use it in 5.7x28 mags, a straight wall .30 caliber cartridge that can be used in something like a p90 mag, I’m picturing the performance to be similar to 30 carbine
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Why not just use .30 Carbine? 7.62x33. Only 5mm longer than the 5.7 based .30 cartridge.
Anyone ever experiment with .30 Carbine using bullets other than 110gr round nose?
The .22 MMJ Spitfire was a .30 Carbine case necked to .22. There was a brief flurry of activity with this cartridge in rebarreled M-1 carbines. Made a handy, light walk-around varmint rifle.
The .22 Spitifre looks just like a slightly enlarged 5.7x28.
 
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tiriaq said:
Why not just use .30 Carbine? 7.62x33. Only 5mm longer than the 5.7 based .30 cartridge.
Anyone ever experiment with .30 Carbine using bullets other than 110gr round nose?
The .22 MMJ Spitfire was a .30 Carbine case necked to .22. There was a brief flurry of activity with this cartridge in rebarreled M-1 carbines. Made a handy, light walk-around varmint rifle.
The .22 Spitifre looks just like a slightly enlarged 5.7x28.
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If memory serves, .30 carbine is semi rimmed and needs a curved mag after so many rounds, thus out goes the idea for a 30 caliber p90, plus those extra 5mm make a huge difference in the hand when chambered in a handgun like the LAR grizzly, in my head it ends up being a straight wall rimless.30 caliber cartridge capable of, albeit with some modifications, being used in common available (at least in the states) magazines like the p90 fn5.7, s&w m&p 5.7 ect
 
The ancestor of the .30 Carbine is the .32WSL, which is semi-rimmed. The Carbine round isn't.
In your first post you made no mention of the type of firearm the suggested cartridge would be used in. A 33mm case vs a 28mm case would make a difference if the magazine is going into the grip of a handgun. The Kimball .30 Carbine pistol was an interesting design that wasn't particularly successful. Its operating system was unusual.
 
fightinghamster said:
Was hanging with the bys today talking nonsense as one does and I had a thought, since 300 black out is just .223 necked up to .30 caliber. And 5.7x28 is essentially mini .223 (the bullet diameters are even the same), what’s to stop some enterprising young lads from necking up 5.7x28 to .30 caliber (probably using 30-30 or 7.62tok bullets) and having a 30 blackout, 28 fury? We’ll workshop the name, outside diameter of 5.7x28 is .311 so a .309 bullet should fit no problem, I don’t have the machine tools necessary to experiment with this, but it’s a nice thought, anyone care to weigh in? Has this been done and failed? Never been done? Feel free to chime in
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7.65 Luger.
 
I dont have the brass handy but I am pretty sure a .30 bullet isn't going into a x28 case without serious issues. The case walls and OD are too thin to make it to .30. If you managed to make one with a super thin neck it would be straight walled and offer nothing to almost anyone that something else doesn't do better.
 
BLCB said:
I dont have the brass handy but I am pretty sure a .30 bullet isn't going into a x28 case without serious issues. The case walls and OD are too thin to make it to .30. If you managed to make one with a super thin neck it would be straight walled and offer nothing to almost anyone that something else doesn't do better.
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I think you're right - base/shoulder dimension on 5.7x28 is .313", whereas neck diameter on 308win is .3433".

You'd only have what, 0.0025" of brass surrounding the 308cal bullet? Necks would split on the first shot if they didn't split in the loading stage.

And what bullets would you use? Not rifle bullets. Even 30-30 bullets would be too hard for the velocity you're going to get from such a small case. You'd be left with what, tokarev bullets?
 
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