I 've killed lotz of Whitetails ,with various calibers ,375 Win., 356 Win, 35 Rem.. 45/70, 9.3X57,9.3X62, 30-30,270 Win. ,30-06, 6.5X55, 243 Winny,8mm Mauser,8mm/06, 357 Mag, 44 Mag, 44 Spl. ,12Ga Shot gun w/ buckshot and slugs, and a 22 Mag.
But the fastest i've ever seen a deer go down was shot by a 11 Yr. old boy with a Rossi singleshot rifle in 7.62X39 with factory 123 gr. Rem. soft point bullet....honest it went down as if it was hit by the Hammer of Thor ! It was a cervical spine (Neck) shot at about 125 Yd.s
But sometimes if a deer has its adrenaline going they will run ...and.. run... no matter what you hit them with..