could be as simple as getting the wind knocked out of you.Maybe some dont get the wind knocked out and some do.Deer that drop from a lung shot are not dead yet, but inabout 5 to 10 seconds they will be. Bullets do have some energy but the 2000 ft/lbs is a load of crap. A bullet will not move 2000 lbs one ft. bullest strike with around the force of a fist or a fastball. There is something definately being transfered, and this usually occurswith the faster you push the bullet. I shot a rabbit with my .22 hornet and literally exploded, fire the same 45 gr bullet at .22 LR speeds and it wont do that.