Grendel LMG

[stanc]

A steel penetrator design based off the 7N6 or 7N10 would facilitate the same velocities as a standard FMJ. Just look at the 5.45x39 velocities for those at 2900 fps out of a 16.3" barrel, with projectile weights at 56gr. M4 with M855 62gr out of 14.5" barrel is 2900+ (not the British down-loaded weak ammo for the L85, but full-power M855). A 120gr 6.5 running quick with the narrow steel rod would smoke some steel.

Okay, you confused me with the "narrow steel rod" comment. The 7N6 or 7N10 design is what I had in mind.

(53gr 7N6 below. 56gr 7N10 reportedly has a longer steel core.)


If I calculated correctly, scaling up would make a 6.5mm "7N10" bullet weighing 97 grains, with ~1.24" length. A little tweaking could probably increase weight to 100 grains, without increasing length. Such a lightweight bullet could be pushed @ ~2750 fps from a 20" barrel, thereby matching 7.62 muzzle velocity. But, would BC be high enough to match 7.62 trajectory?

Lengthen the bullet to the 110gr "sweet spot" for 6.5 Grendel, and it'll extend much deeper into the powder space, causing a double whammy against MV. Would the increased BC of the longer, heavier bullet be enough to offset the reduced velocity?