The Marine Corps has a revolutionary cartridge sitting right in front of them waiting for them to scoop it up and they haven't done it yet. The same critique applies to SOCOM, SWAT Teams nationwide and the bad boys in the FBI, CIA and the other gun groups.
Why hasn't anyone adopted the 300 Black in the 115 grain for their service rifles?
It hits harder than an AK, is just as accurate as the 5.56 and you basically have a new harder hitting weapon that has the exact same manual of arms and operating features as your legacy weapon. The Marine Corps Marksmanship Unit and the Marine Corps Gunners should study the possibility and determine whether it's cost effective/is an actual improvement over the long serving 5.56. I think they'll be pleasantly surprised.
Sidenote: SOCOM/MARSOC should be all over the suppressed version of this round.