Has 6 ARC met its match? The 6mm MAX

**pinzgauer** · 09-26-23, 00:46

Did some reading... maxx is slightly rebated and claims the same case capacity as spc and grendel.

So bigger case head/ diameter than 5.56 but less than grendel/spc. So can run at 54-55k psi rather that 52k.

Should be interesting to watch. Some are very skeptical of usable case capacity with real world bullets at realistic OAL.

**caporider** · 09-26-23, 07:22

Originally Posted by pinzgauer

Did some reading... maxx is slightly rebated and claims the same case capacity as spc and grendel.

So bigger case head/ diameter than 5.56 but less than grendel/spc. So can run at 54-55k psi rather that 52k.

Should be interesting to watch. Some are very skeptical of usable case capacity with real world bullets at realistic OAL.

Case head diameter is .378, same as .223/5.56.

**pinzgauer** · 09-26-23, 07:53

Originally Posted by caporider

Case head diameter is .378, same as .223/5.56.

From the BC precision site:

Code:

Our case is only slightly rebated for a well balanced cartridge maximizing capacity and 100% reliability.

Maxx is based on the 350 legend, which has a case diameter of 0.39". From TFB:

Code:

The .350 Legend is NOT based on the .223 Remington case. It is not a blown out straight walled .223/5.56. This cartridge has a completely new case with a slightly larger base than the .223 Remington, however, its rim is rebated to .378″ diameter – identical to the rim diameter of the .223 Rem. Obviously, the rebated rim is incorporated into the .350 Legend case design to allow using standard AR-15 .223/5.56 bolts with this new cartridge.

https://www.thefirearmblog.com/blog/...end-cartridge/

**Disciple** · 09-26-23, 11:17

Originally Posted by pinzgauer

Did some reading... maxx is slightly rebated and claims the same case capacity as spc and grendel.

So bigger case head/ diameter than 5.56 but less than grendel/spc. So can run at 54-55k psi rather that 52k.

Should be interesting to watch. Some are very skeptical of usable case capacity with real world bullets at realistic OAL.

The 6.8 SPC already has a 55kpsi SAAMI spec at 0.422" head diameter so no gains there, and I don't see how a 0.390 case can match the practical capacity of the 24 GPC.

**1168** · 09-26-23, 11:38

Originally Posted by caporider

Case head diameter is .378, same as .223/5.56.

That’s the rim, not case head.

**mexica** · 09-26-23, 11:56

Isn't the case longer, preventing it from using some of the longer and heavier higher bc bullets?

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**caporider** · 09-26-23, 13:15

Originally Posted by 1168

That’s the rim, not case head.

You're right - got my terminology wrong.

**TAZ** · 09-26-23, 18:15

Interesting, but given that last week was the first box of 6ARC I have seen in the wild, some wildcat that has even less industry support than 6ARC is not going to get much traction. Maybe for hand loaders and such, but for the rest of us its nothing to meaningful for a while. Like the possibility of not needing a new bolt or even having a bit more robust a bolt than what the 6ARC/6.5g use, but at this stage I just want to see ammo available.