Bet-your-life reliability in a 6.5 Grendel AR15 platform?

[Double Naught Spy]

The AR platform is made to feed 223 size cartridges.

Anything else would probably be less reliable.

This would suggest that any deviation from the original design would make the gun less reliable as well given that the deviation isn't part of the original design. Fortunately, many designs such as the AR15 allow for considerable variation, often with the replacement of appropriate parts to make it just as reliable as the original. The notion of original design is fraught with design intent implications and those are often meaningless to the grand scheme of what happens in the field and real world.