The reason the m4 is a smaller cartridge is that its predecessor had serious over penetration issues. Ideally the bullet will stop inside of the victim.
The XM7 will have seriously worse performance due to over penetration and other ballistics, not to mention heavy and limited ammo. Maybe it will fare better against armor, which would be good in a hypothetical matchup with a comparable enemy, but that is unlikely to occur any time soon.
The reason the m4 is a smaller cartridge is that its predecessor had serious over penetration issues. Ideally the bullet will stop inside of the victim.
The XM7 will have seriously worse performance due to over penetration and other ballistics, not to mention heavy and limited ammo. Maybe it will fare better against armor, which would be good in a hypothetical matchup with a comparable enemy, but that is unlikely to occur any time soon.