New Army "Caliber Configuration Study"

[Tony Williams]

Your comparative graphs are not only for a more powerful cartridge, you've also assumed a 20" barrel length for all calibers. The first assumption is obviously not applicable to 6.5 Grendel,

You rather missed my main point, which was that a military-standard 7g lead-free 6.5mm bullet could perform quite close to an 8g lead cored equivalent in terms of velocity and energy retention plus wind-bucking ability, and distinctly better than the M80 in these respects.

Anyway, the muzzle velocity I assumed of 800 m/s for the 8g bullet is actually close enough to what the Grendel can achieve (777 m/s for 8g from a 20" barrel - a reduction in MV of less than 3%) to make a useful comparison.

...and the second does not apply to a "Grendelized" M4 carbine, M27 IAR, and M249 LMG.

The comparisons we are making here are with the 7.62mm weapons, since it was John's comment about that I was responding to.

The question is what performance would 6.5 Grendel deliver with a 7g/108gr bullet, when fired from probable barrel lengths of 14-18 inches? Would a 65G M249 with 14" or 18" barrel come even close to matching M80 performance from the 20" barrel Mk48?

I have assumed in the charts above that dropping the bullet weight to 7g would increase the MV to around 840 m/s - a conservative estimate, since if the muzzle energy remained exactly the same the MV would be 855 m/s.

I'll leave it to the Grendel experts here to calculate what velocities their cartridge could push a 7g bullet to from different barrel lengths.