The mass of the bullet and its velocity together determine its ballistics. Think of it like an MVA where a vehicle hits a stationary object. Two vehicles are the same physical size (caliber) but the second one (30-06) is going considerably faster and is heavier. The second one (30-06) is going to do significantly more damage. There are other factors involving the projectile's properties (bullet or vehicle) and the target itself that can enhance or reduce the damage incurred, but that gets more complicated than simple ballistics.