I realize the 5.56mm has become so deeply rooted in international arms, it is not likely to fade away in my lifetime. Fragmentation due to yaw and cannelure is sort of a bonus, not by design. Penetration leaves something to be desired unless using specialized ammo. It is a fine round, but probably not the best for its intended purpose; combat from 0-600m. The 7.62 has some advantages, but it's not the solution.
What do you educated individuals think would be a viable next-generation round? I've heard .270 and .243 bounced around. The new .270 Short Magnum has some great ballistics and is not much heavier. There are some nifty wildcats as well.
Leave compatibility out of the equation. Assume that if the new round makes the grade, then calibrated scopes will be produced to support it, as well as plenty of magazines and peripherals.
I guess it should be reasonably light, have a nice, flat trajectory, accurate to 600m, reliably produce wound dynamics SUPERIOR to the 5.56mm, and have superior penetration as well: i.e. it will penetrate windshields and 8" diameter trees. Modern technology can design appropriate recoil dampening, but insanely hot loads should be avoided.
I'm curious as to whether there are any existing loads with potential. This is purely hypothetical, but it led to an interesting conversation the other day, so I thought I'd run it up the flagpole here.
SIEGE