i read an article that said that split second is related to the animals heartbeat, the impact of the bullet causes an rush of blood to the brain if i remember right.

i got box of the ballistic silvertips a couple years ago for my 7MM on sale and have shot probally 5 deer (4 mulies/1 whitetail). i'm no bullet expert but i noticed major fragminatation of the bullet. penetration was fine, downed all animals with no problem but noticed blood streaks through the animal from fragmination.