What if the AR15 had not been created?

[stanc]

Maybe, maybe not. There might be a cartridge similar to the Grendel developed in response to the perceived weaknesses of the .224 projectile, but the Grendel is designed around the limitations of the AR15 package. A different rifle might not have the same limitations, allowing a cartridge with a little more snoose, whether through higher pressure or a little larger case capacity.

That's sorta nitpicking. The .224 Springfield cartridge is a hair longer than .223 Remington, but it has the same case diameter. So, an alternate history "6.5 Grendel" undoubtedly wouldn't be exactly like the present one, but for all practical purposes it'd be the same cartridge.

The thing the AR15 has that makes it somewhat unique is its modularity. Anybody with a modicum of mechanical ability, a special tool or two, and a credit card can put one together on their kitchen table. You can't say that about the M14.

Excellent point. That also applies to small gun companies like AA. Chances are, Bill Alexander would not have started a business to market .50 Beowulf M14 or T25 clones, which are more complex and difficult to manufacture. If there had been no .50 Beowulf, there would likely have also been no 6.5 Grendel.

It does appear that 6.5 Grendel's existence is directly and inextricably (Always wanted to use that word! ) dependent on creation of the AR15.