Grendel as a Universal Infantry Cartridge

[stanc]

We need to know two things: Case Volume and Max Operating Pressure.

As I noted, the 6.5x45 rounds I referred to are "stretched" versions of 6.5 Grendel, therefore case capacity is greater. By how much, I don't know, but enough to give a claimed MV in the realm of 100-200 fps faster, IIRC.

I haven't participated in the discussions for some time, but some attention should be paid to starting with the 25 Remington or 30 Remington case. This one can give the same volume as the 6.5 x 45 but with the same head diameter as the 6.8 SPC. It gets this with a somewhat longer case, but one that can still function within the 2.8" length of the 7.62x51.

Yes, there is one member of Tony's MG&A forum who has been developing a 6.8mm round based on the .30 Remington case. I think it's a 6.8x50, with 2.8" OAL.

The round count in a magazine of the same depth will be greater than either the 7.62x51 and the 6.5x45 and will likely be enough to make it attractive.

I doubt that. There is no difference in round count between the SPC and Grendel case diameters for magazines of the same height as a 30-rd 5.56 mag: Both have 25-rd capacity. For SPC vs 7.62, it would be 25 rds vs 23.

When you get up to 30-rd capacity for the SPC, the Grendel might be limited to 29 rds, an insignificant difference that could be compensated for by increasing mag height a mere third of an inch.

A 6.5x45 made on a "stretched" Grendel (or shortened Carcano) case not only allows a more efficient case configuration than a 6.5x50 built on a .30 Rem case, it also offers the advantage of a shorter magazine with resulting better ergonomics, and the potential for rifles and machine guns with shorter receivers (for lighter weapon weight).