Alternative to 6.5 Grendel?

[montana]

Okay I get 2, but could you not chamber the KAC PDW in the 5.56 NATO and have a 4.5lb 5.56 PDW?

I don't know, the KAC Personal defense weapon uses dual short stroke gas pistons. I was more interested in the cartridge concept than the rifle. LRRPF52 was suggesting it was possible to duplicate or exceed the 5.56 NATO performance from the .221 Fireball case and I thought of the 6X35 round.