Has anyone tried to do an improved 7.62x39? I've been thinking the same thing, moving the shoulder to 30 degrees and a body taper closer to 22PPC. I'm not sure if it would be worth doing, although if you could still shoot factory brass ammo you'd gain a bit, and the change would be trivial - about as complex at 22 k hornet.
I've been looking at 6.5 grendel too, but haven't found a good barrel blank as a starting point.
Anyone interested in a 7.62x39mm improved, please contact me. I'm working on designing a spec, and will order a custom reamer and dies. Would like input.
