Optimized Caliber

[stanc]

If you are designing a new chamber and rifle, then the bolt thrust issue is a moot point, you can run whatever pressure you designate as the ideal, and build the bolt assembly to match.

That's true, but less beefing up of the bolt and other components will be needed for a cartridge with less bolt thrust. That translates to increased durability and/or decreased weight.

The longer, skinnier 6.8 case requires a longer extraction movement, with the attendent larger recipricating issues, which creates at least as big a disadvantage as does the ability to make links work for the shorter, fatter case.

Do you seriously think that a 4mm longer extraction poses anywhere near the difficulties as design and development of a new link???

We know that full auto is no issue with the Grendel because its been run that way in AR's by plenty of people...

We know that 6.5 Grendel does full-auto fine in magazine-fed rifles. We do not know how it does in belt-fed machine guns.

Heavier doesn't necessarily equal better penetration. At equal velocities, penetration also is affected by frontal area, so a bigger bullet that is heavier might have the same penetration as a lighter, but higher sectional density bullet.

And once again, using same weight bullets, the Grendel has a higher SD, and thus will penetrate better.

The problem with that idea is, with the 5.56 mag length limit lifted (as in Paul's LMG concept), 6.8 SPC is not limited to bullets of the same weight. It could use bullets of the same SD, launched at equal or higher velocities.