Words such as “slow” and “massive” are relative. The difference in muzzle velocity between a 9mm, .40, and .45 is a few hundred FPS. While a .45 round can be traveling as “slowly” as 850 FPS, it’s still fast enough to arrive at a target within handgun range far more quickly than any living target can move to avoid impact.
As far as impact energy being “massive” — the assertion suffers from three problems:
1) No handgun round imparts “massive” energy. Even the stupid calibers (e.g. .50) barely exert enough force to move a grown adult (the full force of any bullet is transmitted to the shooter as recoil. A gun you can hold and fire in one hand). While it might hurt your hands, it’s not as “massive” a force as being struck by a 10 lb sledge swung by gorilla.
2) “Impact energy” isn’t what slows or stops a person or animal. Rather, it’s the amount of damage imparted to an essential component of movement, thought, and/or will. Movement can be degraded by damage to bone, nerves, or muscle. Thought can be degraded by damage to the central nervous system. The Will can be degraded as the recipient of the bullet reconsiders the action that resulted in a bullet impact.
3) Handgun bullets are small — they penetrate and pass through muscle and/or organs, and are sometimes stopped by or shatter bones. The “impact” is a small part of the equation of damage and incapacitation. If we could design a handgun that fired the head of a ten-pound sledgehammer at Gorilla-capable velocity, we would be carrying those. But the size of the magazine would make the handgun unwieldy and inconvenient. So we carry little guns with little projectiles because they have proven reasonably effective at slowing and sometimes stopping threats. Line up all the popular handgun rounds according to size and you will see there’s not much difference.
