What if the AR15 had not been created?

[ofreen]

Would the 6.5 Grendel cartridge never have been developed?
(snip)
We might not have an AR15, but we'd likely still have 6.5 Grendel.

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.

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. This aspect has probably kept the Grendel afloat up until now as much as any particular characteristic of the cartridge.