Perhaps this question involves too many factors to consider and lends itself to being overly speculative but... What would seem to be the most important ballistic property of a bullet in determining lethality? (coming from another forum trying to get an answer from a more qualified group - question has come up in the past a few times with no one giving a very good answer) Muzzle velocity, energy and bullet weight are typically published figures. Many people seem to say bullet weight is most important (maybe suggesting that bullet momentum is the key factor?), others say a high caliber is most important, etc. After thinking about it for a while I've come up with 2 factors I would think would be most important for immediately destroying a target. 1) Projectile energy 2) Projectile expansion upon hitting target/projectile size My thinking on these 2 is the projectile will develop high power since power = (force * distance) / time where force is force exerted on target by projectile The projectile expanding on contact with the target would cause in increase in df/dt, resulting in higher peak power (but trailing off more rapidly as due to more rapid loss of velocity). So since there would be higher peak power, or higher rate of energy transfer, I would think this would be analogous to torching a piece of meat to crisps in a few seconds Vs. heating it in a crock pot for a longer time. Of course that brings the question exactly what sort of damage will that energy cause, if any... This would lead me to believe that large, light, extremly fast bullets that expand to large sizes rapidly should do the most (immediate) damage... Can anyone provide insight? Again, sorry if this is too speculative but there are many myths in this area. It would be nice to know the truth.