I have an AR in 6.5 Grendel. You can change the barrel, bolt carrier and magazines on an existing AR and you have a rifle that has an effective range of 800 plus yards. It pretty much equals the overall ballistics of the 7.62 NATO at that distance. You sacrifice little in magazine capacity and the recoil is much lighter than the 7.62. Accuracy is excellent. It is an good round for hunting deer size game so it will drop a enemy soldier in his tracks.
6.5mm seems to be the big winner in long range competition shooting.
Back when the FN FAL was being designed, the British were wanting something along the lines of a 7mm but the US DOD was rather insistent on using a .30 caliber projectile. The FN FAL was thus produced using the 7.62 NATO standard round which was not what anyone really wanted. Then the US DOD went with the M14 anyways while everyone else in NATO carried the FN FAL, now chambered in a round that was too big for it (in full auto mode anyways).
Time went on and the FN FAL went on to become the right arm of the free world and the M14 went on to become the M16 now chambered in 5.56mm. Yes, after all of that drama, we ended up adopting a 5.56mm round.
Now, 50 years later, we’re back to wanting something bigger than 5.56mm but not necessarily as big as the 7.62 NATO round.
something like the 280 British perhaps?
We should have just gone with the .280 British FAL and been done with it. It’s like the British say, “the Americans can always be counted on to do the right thing...after they have tried everything else first.”