How could or should the 6.5 mm Grendel be improved?

[Trooper]

I am not exactly sure at present. The result will stem from the target definition and the hit probability ie the required carried kills.

Gut says maybe a 6.5 but i would prefer a 7. Keep the OAL short and then work back to the case volume for the optimum operating pressure at an acceptable fill level with the new powders.

Grendel in the legacy M4 runs at too low a pressure to best utilize the case. I would want to push this up. The technology for this is simple and the bolt/barrel extension geometry is not a problem. The extension/barrel interface might need some massaging to hold up at elevated temps. In a new rifle this is easy stuff and the weight spiral is non existent as long as the mag length is constrained.

The 7mm UIAC is too much like the .280 British (7x43). While I like the 7mm, it does have more recoil (heavier bullet) than the 6.5mm. The one thing that is coming out from my research is that the 6.5mm is at the optimum point among calibers. It has the sweet spot in terms of BC and sectional density. While the 6.5 and 7 are not the best with respect to magnum calibers (too much barrel wear), they are great when comparied to the 7.62x51 or the .30-06. We have the 6.5x55 Swede as the baseline. If we take the .260 Remington (6.5mm-08 with a 140gr bullet) in comparison to the 7mm-08 (162gr) or the 762.x51 (192gr), the 6.5mm comes out strong. It gives similar down range performance with far less recoil.

This whole question would have been moot had the US gone with the .280 British and the FAL back in the '50s!