Great addition to the thread. Very well thought out opinion. I agree with all you said, accept the body armor thing. The full pressure stuff is not available yet, as the Fury is low pressure stuff, no real gain. Which brings up another logistical nightmare: +P stuff for front liners and "regular P" for everyone else and storage? Steel armor will defeat it no doubt, composite armor, not so sure.
Armor really is only effective while standing squared up to the shooter, not at all effective from the side, or in the prone, which adds to the dumbness of the "armor piercing" requirement.
I would rather be light and fast, but that is just me.
If I remember right, military standard for the M4 was 4 MOA. Way above civilian "standards". The 277 in full pressure flavor will destroy barrels, no doubt. But what's money right??.... especially when you can spend someone elses.