Pondering the "magic" caliber.

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Lots of interesting ideas here. Two cartridges mentioned in particular are the .357 SIG and the 38-40. Both are based on necking down a larger cartridge. Another is the 10mm Auto. Plenty of oomph there. I think it would be a good carbine cartridge. Comparing the three, I wonder about the 9 x 25 Dillon and how it would perform in a carbine. By tweaking it a little so you could load .357 diameter bullets vs. .355 I think you could really expand the versatility. Maybe someone has done it.
I kind of think you missed one. In my mind, the 7.62x25 is really just a necked down 9mm, but since the 30 Mauser was first, I guess my opinion may not be historically correct.
 
I like the OP's question and have thought about this myself. So I'm thinking a pistol and a carbine that could both use the same cartridge and same 10 to 15rd mag would be great. I have a PCC 9mm for this reason. But I want the carbine to shoot a 150gr bullet at 2600fps and the pistol to be able to shoot the same round at 1600 or so:)
 
I wonder how long/heavy a bullet you could load if you necked the 10mm down to 7.62/.308 instead of .357 ?

Dangit! Now that's going to be on my mind.

I purposely left the 7.62 x 25 out because (probably subconsciously) I was focused on .35 caliber bullets. Now I'm going to have obscene images of long skinny things going through my head.
 
I like the OP's question and have thought about this myself. So I'm thinking a pistol and a carbine that could both use the same cartridge and same 10 to 15rd mag would be great. I have a PCC 9mm for this reason. But I want the carbine to shoot a 150gr bullet at 2600fps and the pistol to be able to shoot the same round at 1600 or so:)

Those are impressive numbers. Anybody know what a .357 AMP can do?
 
I like the OP's question and have thought about this myself. So I'm thinking a pistol and a carbine that could both use the same cartridge and same 10 to 15rd mag would be great. I have a PCC 9mm for this reason. But I want the carbine to shoot a 150gr bullet at 2600fps and the pistol to be able to shoot the same round at 1600 or so:)

Since you put numbers up, and the idea of a .30 caliber bullet in my poor noggin, a round nose projectile for the 30-30 came to mind. Because my Hornady manual was handy, #3035 weights 150 grains, has a ballistic coefficient of .186, and the muzzle velocity range is listed as between 1800 and 2500 fps. Those numbers are close to what you describe. I didn't find any handgun bullets that seemed to match as closely. Then again, I just looked at Hornady. The trick is to figure out the rest of the cartridge and something to shoot it with.
 
I've often thought .357 mag. had a lot going for it as it can be chambered in revolvers and carbines, with respectable ballistics from both (emphasis carbine, not rifle). And I've often thought that a Ruger Camp Carbine style tube mag. autoloader in .357 would hit a sweet spot out there.

So I've been wondering why:
1. There aren't detachable box mag. carbines out there that shoot a more "potent" hand gun round, that could be chambered in a auto-loading pistols (with a more reasonable grip length).
2. There are so few auto-loading hand guns out there that shoot a good carbine round. (The only ones I can think of are the Coonan in .357 mag. and the Auto Mag III in .30 carbine)

Granted, I may be "small minded" in my thinking, but from my perspective AR pistols aren't really pistols and 9mm luger and .45 acp carbines don't cross the "respectable ballistics" threshold.

Rimmed cartridges seem problematic for reliable feeding from a detachable box mag.

And 33 mm appears to be too long for a reasonable grip frame length on an auto-feeding pistol.

I'll nominate 9x23 Win. for consideration... but have never seen a carbine chambered for it.

Curious to hear other's thoughts on the topic.
It's called the .357 Sig.
 
@SSN Vet, I think your note about rimmed cartridges explains most of it. As for the rest, it may simply be a small enough market that the manufacturers aren't particularly interested. Otherwise the .357 Sig and the 10MM might both be more popular cartridges.
I agree .
Also the only way it would be a viable option for 357 would be if they offered 357mag rimless. Kind of like they do the 45 auto rim brass.
That leaves us with 38 Super as another viable option.
 
I agree .
Also the only way it would be a viable option for 357 would be if they offered 357mag rimless. Kind of like they do the 45 auto rim brass.
That leaves us with 38 Super as another viable option.

I had some vague memory of a rimless .357 (turns out it was the .357 AMP, mentioned upthread) and came across the .357 Rimless. I have no idea if the thing is available (or if everyone but me knows about it - I don't follow AR-15 developments at all) but it looks like another candidate for the OP's list.
 
I think the 9x25 Dillon and .40 Super would both be pretty interesting chambered in an AR. The bottleneck cartridge should feed well and some pretty impressive velocity would be possible out of such a carbine.
 
I would like something like a Deerfield .44, but in .50. Bonus points for using Desert Eagle magazines.
I have the Desert Eagle for the pistol…:)

There are a few gunsmiths who have done conversions of Marlin 336s to 50AE and possibly 500 Linebaugh. I am not sure of the ballistics though.

Personally, the idea of a common round that shoots 2600fps from a rifle and 1600fps from a pistol seems like a lofty goal with even loftier expectations of the laws of physics.
 
Personally, the idea of a common round that shoots 2600fps from a rifle and 1600fps from a pistol seems like a lofty goal with even loftier expectations of the laws of physics.
I agree. A hundred feet per second per inch of barrel is, optimistic. Especially so in a straight walled cartridge, or a cartridge that still fits lengthwise in one’s hand.
 
I've often thought .357 mag. had a lot going for it as it can be chambered in revolvers and carbines, with respectable ballistics from both (emphasis carbine, not rifle). And I've often thought that a Ruger Camp Carbine style tube mag. autoloader in .357 would hit a sweet spot out there.
A really careful look at the 10mm reveals that it and the .357Mag are virtually clones. The 10mm tops out a bit higher for momentum with heavy bullets. The .357Mag tops out a bit higher for energy with light bullets. But the differences are small. Over most of their performance range they are very similar.

That's in handguns. In longer barrels, the .357Mag does seem to have an advantage, but probably not enough to justify it over the benefits that a 10mm would provide in an autoloading design.
 
I've often thought .357 mag. had a lot going for it as it can be chambered in revolvers and carbines, with respectable ballistics from both (emphasis carbine, not rifle). And I've often thought that a Ruger Camp Carbine style tube mag. autoloader in .357 would hit a sweet spot out there.

So I've been wondering why:
1. There aren't detachable box mag. carbines out there that shoot a more "potent" hand gun round, that could be chambered in a auto-loading pistols (with a more reasonable grip length).
2. There are so few auto-loading hand guns out there that shoot a good carbine round. (The only ones I can think of are the Coonan in .357 mag. and the Auto Mag III in .30 carbine)

Granted, I may be "small minded" in my thinking, but from my perspective AR pistols aren't really pistols and 9mm luger and .45 acp carbines don't cross the "respectable ballistics" threshold.

Rimmed cartridges seem problematic for reliable feeding from a detachable box mag.

And 33 mm appears to be too long for a reasonable grip frame length on an auto-feeding pistol.

I'll nominate 9x23 Win. for consideration... but have never seen a carbine chambered for it.

Curious to hear other's thoughts on the topic.
What about 5.7x28!
 
With the 2600 fps/1600 fps criteria, you might get that out of a 10mm using 135 gr bullet. But I think thats a light for cartridge weight bullet. I would be ok with a 175 ish gr bullet at 1400 fps out of a pistol and maybe 1900 fps from a carbine length barrel.
 
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