New Army "Caliber Configuration Study"

[Tony Williams]

Stan, no, I do not think a green 6.5mm 108gr lead-free can compete with standard 7.62x54R PKM ball.

I'm not so sure. A green bullet is certainly unhelpful and 6.8mm may be a better choice, but 6.5mm should still work. I ran some data through the JBM calculator to compare the ballistics of 6.5 mm 8g/123 grain (lead core) and 7g/108 grain (green) bullet with the 7.62mm M80, assuming that both bullets' form factor would be the same as that of the 5.45mm 7N6 (.929 for the G7 FF, according to the BRL), therefore resulting in G7 BCs of .271 and .237 respectively. Some of the graphs below from this article illustrate how these compare (with 5.56mm M855 thrown in for fun):









The 6.5mm cartridge which I assumed in the above is a tad bigger than the Grendel, stretched to c.45mm.