Hit point system when applied to living organisms clearly represents lethality in real life. In very inaccurate way but still. In real life lethality comes from ability of the projectile, or object in general to cause damage to vital parts of the body. That's not caused by kinetic energy alone. It's much more complicated than that. You have to factor shape, weight, ability to change shape upon impact or to fragment, and other things. And of course it factors which part of body it impacted.
There is no general agreement what lethality is, most importantly because it can be something different under different conditions. But for the case of comparison to Fallout game mechanic, size of the wound that bullet cause to living tissue, both it's diameter and it's length (penetration) can be used as a measure:
"...when was the last time that the cause of death was listed as "kinetic energy?" Surely in the combined annals of recent history this accepted cause of instant demise must be at least hinted at in obituaries and autopsies?
Of course it isn't, with far more historically popular listed causes of death being such maladies as "consumption." In lieu of flowers, perhaps we should ask that donations be sent to the Kinetic Energy Foundation chapter near you?
Kinetic energy is a poor basis for anything specific, as is velocity alone, mass alone, or any number. Can you look at the carcass of a game animal and determine what energy was "transferred" to it? Ironically, "high energy" projectiles have left wounds on battlefields that need no surgery at all; no excision of tissue."
"The horrific error in putting your faith in either kinetic energy or a Taylor Knock-Out value should be obvious. If you believe in TKO, a 12 gauge Foster slug is 13 times more deadly than a .223 Remington, almost four and one half times as lethal as a 30-30, and over 350% more deadly than a .308. It would also characterize the .22 LR rimfire as virtually worthless, though it outpenetrates our .223 Remington round, our 12 gauge Foster slug, and remains the most popular professional assassination cartridge of all time. Does anyone believe that?
The kinetic energy figures are also misleading. They would lead you to believe that the Foster slug is far superior to a 30-30.
The wounding ballistics show that the destruction of tissue by the .308 is superior to the rest of the pack, and that the load that offers the best penetration of the bunch is the .30-30. These two cartridges are clearly superior to the others--a conclusion that will not be surprising to experienced big game hunters. It is easy to fall into the trap of confusing trajectory with lethality, and accuracy with projectile wound profiles. Wounding ballistics profiles have nothing to do with either."
"The relatively modern broadhead arrow, with less KE than a .22 Short (50 fpe) has been used to kill all species of game. As Dr. Fackler wrote in 1987, "It is difficult to be optimistic for the future when these weapons developers still use the scientifically discredited "kinetic energy deposit" method to estimate wounding effects."
The idolatry of velocity alone greatly misleads, and kinetic energy deposit has been clinically disproved. Yet muzzle velocity and energy are still used today as the most common guides to attempting to predict wounding performance."
"Thanks to the human races' continued proclivity towards killing off parts of itself, we know that foot-pounds of energy is a myopic way of describing projectile effectiveness. How much kinetic energy does it take to stick a knife or spear between the ribs of a game animal?"
http://www.chuckhawks.com/energy_transfer.htm