2.3" or shorter cartridges made from 12mm/308 brass?

[justin22885]

just wondering if anyones aware of any good cartridges that have a common 12mm base diameter that can be made from 308, 30-06 brass etc, but is short enough to fit an AK/AR length action?... the idea is to have a smaller carbine chambered in a caliber that can share all the same inexpensive, common reloading components of something like a .308 or 6.5 creedmor.. 5.56 brass doesnt have enough volume or performance desired and 7.62x39 is too non-standard in both cases (which are almost always steel) or their bullet size

so any other options?.. 6.5BR, .30BR, 30x44, 7.92x33, etc?

 

[hatt]

You could get a .458 SOCOM bolt and make any .308 based wildcat you wanted. Not sure what you'll do about mags but you may could make something that'll fit in available mags.

 

[justin22885]

.458 socom bolt?.. for what?.. if youre referring to an AR youd have to significantly decrease the pressure so you wouldnt shatter the lugs.. the AR is a bad choice for the type of cartridge im looking for, an AK can much more safely handle the higher pressures of a larger diameter bolt face so this would either be for an AK conversion, or a rifle i design and build myself customized for the cartridge

 

[Gtscotty]

if youre referring to an AR youd have to significantly decrease the pressure so you wouldnt shatter the lugs.

Not really, but you would have to redesign the bolt itself, and the barrel extension. This is exactly what Dtech uppers did to create AR-15's in WSSM calibers (.243, .25, 6.5, .30, .358). It's also what AR performance did to create AR-15's in their new .270 AR caliber (which as it's based off of 6.5x47 Lapua, uses the same case head size as .308). AR performance has done pretty much exactly what you're suggesting, but in .277 caliber... 130gr bullets at 2,800 fps from a 20" AR-15 is pretty strong performance.

 

[justin22885]

well i can simply machine out an AK bolt face by an extra 0.65mm and be done with it, would only need to find a barrel then and without any threads on the AK barrel thats not all that hard to do, just press it in until headspaced, pin it, then locate and drill the gas port hole

ive never heard of .270AR, but if it is based on 12mm brass id certainly like to see and learn more about it but so far i could only find very limited info online.. im also not going to forget about the 7.92x33 as the cartridge already exists, and with an AK length action i could easily get some 150 grain bullets in it without sacrificing case capacity, assuming i could make the mags for it

 

[Gtscotty]

Here is the manufacturer's page on the 270 AR, another page discussing it said you could easily form brass on a press (read: no fire forming) from 6.5 Creed or 6.5x47.

http://www.ar15performance.com/inc/sdetail/11562/14405

EDIT: Here is a post (#3) by the cartridge designer (Constructor) on 68 forums that gives some good info.

http://68forums.com/forums/showthread.php?39692-270-ar

im also not going to forget about the 7.92x33 as the cartridge already exists, and with an AK length action i could easily get some 150 grain bullets in it without sacrificing case capacity, assuming i could make the mags for it

More to the point would be the 30 Remington AR

http://bulletin.accurateshooter.com/2008/10/remington-introduces-new-30-remington-ar-cartridge/

.473 bolt head, impressive ballistics for 2.3" sized cartridge, and already (perhaps formerly) commercially available. I'm not sure if anyone is still making uppers in 30 Remington AR as it was a commercial flop, but if you looked around you might be able to pick up a used copy for cheap. Regardless, it would be much, much easier than making your own 7.92x33 AK, then fabricating your own custom magazines for it.

 

[crazysccrmd]

Using ARP bolts and extensions designed for the .473" case head and higher pressures you can get a .257, .277, .284 and maybe others as time goes by.

 

[justin22885]

even though the .30 remington AR has a 12mm rim, its base diameter is significantly enough larger where it couldnt be made from cheap once-fired .308 brass.. if it could have been, i dont think it would have been as much of a flop, they didnt really make it handloader friendly and the factory ammo for it as well never really picked up

 

[kBob]

How about yea olde .44 Auto Mag?

-kBob

 

[hatt]

.458 socom bolt?.. for what?.. if youre referring to an AR youd have to significantly decrease the pressure so you wouldnt shatter the lugs.. the AR is a bad choice for the type of cartridge im looking for, an AK can much more safely handle the higher pressures of a larger diameter bolt face so this would either be for an AK conversion, or a rifle i design and build myself customized for the cartridge

Of course I'm talking about the AR. You're the one who mentioned the AR. Who'd go through the trouble of having an oddball round in the AK platform.

 

[M1key]

22BR, 6BR, 6.5BR, 7BR, 30BR, etc

M

 

[justin22885]

Of course I'm talking about the AR. You're the one who mentioned the AR. Who'd go through the trouble of having an oddball round in the AK platform.

the AK isnt limited to a specific length/width of magazine or a certain curvature and i dont have to rely on pre-made barrels with factory machined extensions to do a conversion, nor do i have to worry about case heads weakening the bolt or bolt thrust.. quite simply the AK action is more free to customize, it can easily chamber 12mm case heads without weakening the lugs, can be adapted to use a variety of different magazines, and barrels require little to no machining at all, simple a lathe for the most part... so why limit myself to only conversions offered from some retailer when on an AK and basic gunsmithing skills and tools you can do pretty much any conversion you want?

 

[justin22885]

22BR, 6BR, 6.5BR, 7BR, 30BR, etc

M

these are fairly straight walled cartridges with sharp shoulder angles, am i right?.. im wondering how those would function in a semi automatic?.. seems they could be cause for feeding and reliability issues?

 

[M1key]

Don't have personal experience, so I couldn't say...

I did have an Olympic barreled AR chambered in 6PPC that used a 7.62x39 bolt. Maybe use that caliber as a start. It was a bit finicky with mags. Maybe a different follower would have helped.

M

 

[justin22885]

hmm, i guess 7.92x33 or something new would be the only options for a 12mm based cartridge design for a shorter semi auto carbine.. aah, but if i come up with my own, which bullet?.. 30 cal? 7mm? 6.5?

 

[M1key]

How about the 30 Remington AR?

M

 

[justin22885]

30 remington ARs base diameter was too big, otherwise it would have been perfect, not making it from 308/30-06 brass was stupid on remingtons part because not only was no one manufacturing it, they made it hard for people to make themselves too

 

[crazysccrmd]

The problem with a .473 case in the AR is the redesigned bolts and extensions needed to allow for high pressure loading. Once you get around that hurdle you can find some very nice performance.

 

[justin22885]

The problem with a .473 case in the AR is the redesigned bolts and extensions needed to allow for high pressure loading. Once you get around that hurdle you can find some very nice performance.

yeah, those ARs and their limitations.. even if you could get a new cartridge to work at severely underpressured loads or completely redesigning the upper to the point of no longer being an AR, youll still have issues with magazine width

 

[crazysccrmd]

You can get a full 55k psi/.473 case with just a different bolt and extension to match. Nothing else on the AR needs to be changed and all standard parts work just like if if we're a 5.56. Magazines are problematic if you're wanting more than a 5-10rd hunting capacity.

 

[Gtscotty]

yeah, those ARs and their limitations.. even if you could get a new cartridge to work at severely underpressured loads or completely redesigning the upper to the point of no longer being an AR, youll still have issues with magazine width

Kind of dramatic here. As crazysccrmd said, you can get full pressure .473 rim rounds in an AR-15 with a redesigned barrel extension and bolt. With two parts changed it would be ridiculous to call it anything other than an AR-15 with slight modifications. If you really don't like the AR, that's fine, but you mentioned it in your OP. It is going to be way easier to use a development that someone else has already accomplished (modified bolt and barrel extension) to make your vision work in an AR, than to modify a pressed together Ak, then manufacture your own magazines.

 

[Casefull]

The OP seems more interested in pimping the AK than listening to good suggestions for his 'new' cartridge.

 

[justin22885]

well people here seem so adamant i pimp an AR like its the only semi auto rifle in the world, anything i do will be done to a rifle i like better, prefer, and doesnt need special equipment to prevent breaking locking lugs or force me to a specific magazine shape

besides, there doesnt seem to be a 12mm based cartridge of this length that doesnt seem highly specialized for a bolt action with almost no taper and relatively steep shoulders, besides the 7.92x33 i dont think there is one

 

[crazysccrmd]

An AR might have its limitations but the potential for accuracy is much higher than an AK platform. To me that makes it worth the effort.

 

[justin22885]

An AR might have its limitations but the potential for accuracy is much higher than an AK platform. To me that makes it worth the effort.

im not looking for accuracy, and my 5.56 AK gets 2" groups at 100 with M855 which is plenty suitable.. anyway, im not looking to buy an AR