We are all dead!
It’s like a walking advertisement for the full sized MBR (Main Battle Rifle) like the FAL and G3.
Are there 7.62x51mm variants suitably armor-piercing to be reliable against something made substantially of metal and not subject to pain, shock, or blood loss?
I’d assume so, given that the stuff would at least be jacketed for treaty reasons; but ‘facing robotic cheetah’ would be a bad way to learn that your preferred round works on humans because it’s a good anti-meat projectile; but isn’t so hot against robots.
Military ammo is solid and steel cored, only lacking a tungsten tip to be defined as “armor piercing.” As such, it breezes right through generic steel that is not specifically hardened to “armor” specifications. And although the best body armor can stop rounds like that, the damage to the target can still be substantial.
It will be interesting to see it reach the point of being able to operate at better than 50% efficiency with a broken leg, like a real animal. When deer run through the woods, they break a leg pretty often. Hunters often shoot big healthy deer with a big knot in one leg from a healed fracture.