I keep seeing all these new heavy hitting .45 and .50 caliber AR-15's lately.  Why not a .30 caliber?  It seems that it would feasible to reproduce .308 Winchester ballistics with a necked down 458 SOCOM, .50 Beowolf, .45 Professional, etc. And since the case would be very short and "fat" it would burn powder very consistently and efficiently.  I would love to have one!  Anyone else?

Check out www.sskindustries.com/cartridges.html.

I don't know too much about the quality or service, but they have a .300 Whisper cartridge that sounds about like what you're looking for.  Anybody know anything about them.  They're in OH, so I may check them out at some point.

I have a friend that has an AR with a SSK 300 Whisper upper.  With the subsonic loads, he's able to shoot it at indoor pistol ranges.  I don't know much about the caliber yet, but I plan to read up on it soon.  I do know that it's based on a .223 case that's been resized to .30.  Should make an EXCELLENT suppressed weapon.

However, I don't think this is what Wirebrush was talking about.  He wants a short a FAT case.  I have a feeling he's wanting a .458 SOCOM case necked down to .30 cal.  Mybe I'll talk to Marty at Teppo Jutsu about this.  See what he says.

Actually I asked about this to Tony (who came up with the .458).  He indicated there was too much pressure on the bolt lugs - they would shear off.  Large calibers don't have the pressure issue, but as you make the bullet smaller (assuming you are using a .458 SOCOM case so you can attempt to approach .308 velocities) the pressure goes up.

Now if you do want a .30 caliber AR you can get a 7.62x39 or the .300 Whisper (IIRC its also known as .300 fireball or somesuch by Oly and/or Kurt - same dimensions/specs as the whisper - they just can't use the trademarked name).

The .300 Whisper is a .221 Remington Fireball cartridge necked up to .30 cal. The .221 Fireball has the same base dia. (.378") as the .223 but a length of 1.4" compared to 1.76" for the .223. When loaded with the 220 gr .30 cal bullets the .300 Whisper has the same cartridge over-all-length as the .223 with a 55gr bullet.

I've always wanted one.

Quoted: Actually I asked about this to Tony (who came up with the .458).

Tony DID NOT come up with the .458.  He merely marketed and sold uppers for it.

Marty at Teppo Jutsu designed the cartridge.

Quoted: Tony DID NOT come up with the .458.  He merely marketed and sold uppers for it. Marty at Teppo Jutsu designed the cartridge.

Ok whatever - that's irrelavant to the discussion (I only added it so people would know who Tony is).  Still have the engineering issue.

Brouhaha,  Let me know what Marty says will ya?  I assumed that pressures would increase somewhat, but the .458 SOCOM generates 30-06 muzzle energy, so I would think .308 winchester balistics would be possible.  Then again, If it's possible someone should have done it by now rather than building yet another .45-.50 cal conversion.

Wirebrush, back in the "458SOCOM or 50 Beowulf" thread, Marty says this about necking down to .308:

"Necked to 308? Unfortunately, best we can tell, this causes too much bolt thrust and the lugs will shear off the bolt ... I'd love to make it work but haven't found a way yet ..."

Here's the link to the thread, check for his post near the bottom of the page:

www.ar15.com/forums/topic.html?b=3&f=118&t=138513&w=searchPop