Optimized Caliber

[stanc]

With the 6.8, you would want to neck it down to 6.5mm, but a 6.5 SPC or 6.8 SPC with longer projectiles for an LMG would make a COAL close to 7.62 NATO. What I like about the Grendel case is that I can still have a relatively short COAL compared to 7.62, and that means more optimum space utilization on the soldier's load.

The difference in cartridge OAL would be only 0.16" for 6.5 SPC, and ~0.20" for 6.8 SPC. It's hard to imagine that such a tiny amount would be noticeable.

Even if it is, the other side of the coin is the increased bulk of the 6.5 Grendel case makes for a longer belt, or for fewer number of rounds in belts of the same length.

200 - 5.56 NATO
160 - 6.8/6.5 SPC
150 - 6.5 Grendel

The .277 projectiles require way more velocity to get them to do what a moderate velocity 6.5 will do...I learned that with the 140gr 6.5 Berger VLD for my .260 Rem versus the .277 140gr Berger VLD for my .270 Winchester: The .270 requires 250fps more muzzle velocity to match the .260 Rem at 1000yds, and the .260 still has it beat for wind deflection.

That's the same thing Bill said, except in different words. Again, nothing says 6.8 SPC must use the same weight bullet as 6.5 Grendel. The 6.8 can use heavier bullets with BC and SD comparable to those for 6.5, thereby achieving similar trajectory, wind drift, and retained energy.

These factors are what make the Grendel case more appealing to me for an LMG. The one possible advantage I see with the 6.8 case is the shoulder angle might be more conducive to feeding, but the inverted feed ramp of a belt fed would be tapered to articulate with whatever cartridge it was chambered in.

I don't view 6.5 Grendel's 30-degree shoulder as significant. After all, the 7.5 Swiss has a 28-degree shoulder, and it was used in belt-fed GPMGs for many years.

Far more critical is the issue everyone else wants to ignore: There is no empirical evidence to support the idea that viable disintegrating links can actually be developed for 6.5 Grendel. Those advocating a 6.5 Grendel LMG are assuming that proper links can be done. They may be wrong.