Does the 6.5 grendel have the potential to replace the 5.56 for the military?

[stanc]

The FMJ comparison is useless. The military no longer uses standard fmj. They use a steel core AP round. I don't see us being able to do this comparison any time soon.

A relevant comparison would be the 77gr smk load and a 123gr smk Grendel loads from 14.5" carbines. Assuming the Grendel or a variants was adopted, DMRs and special ops guys would be issued a 123gr smk load as it's available to their units. I'd bet the farm on that.

Concur on value of doing 77gr SMK/123gr SMK comparison. However, those are special purpose loads, and would give no useful data regarding performance of general purpose Ball ammo.

I very much disagree that FMJ comparison is useless.

First, a new caliber would almost certainly become NATO standard. Currently, all other NATO armies use FMJ; only the US uses EPR. Given the adherence to Hague Declaration III by other nations, it seems likely they would continue to want non-fragmenting FMJ. Which means that any NATO standard 6.5mm round would probably also be FMJ, with the US using non-NATO 6.5mm EPR, just as it now uses non-NATO 5.56mm EPR.

Second, 6.5 FMJ/5.56 FMJ (or 6.5 FMJ/7.62 FMJ) testing would allow "apples vs apples" comparison of relative performance capabilities of Ball ammo, especially in regards to practical accuracy at long range, and barrier penetration.

Either way the x47 case is to much in terms of needed mag width and recoil.

Recoil, possibly. Mag width, not really. The .264 USA (6.5x47) case diameter is only marginally greater than that of 6.5 Grendel. The difference would be unnoticeable.