The Marine Raiders don't want the HK M27.
https://www.marinecorpstimes.com/new...want-any-m27s/
The Marine Corps Forces Special Operations Command is taking a pass on the M27 after reviewing the new automatic rifle during its initial development. Simply put, the elite Marines were not impressed with the rifle’s ability plug any existing gaps in fire power and they found the weapon’s 16-inch barrel too long.