if youre shooting a zombie so many times, youre making a mistake. when you see a zombie, pop off 3-5 pistol shots. that should be enough to drop them. if not, fire more, slowly, since you dont want to waste bullets. when the fall, try to auto target the zombie. if youre character does so, its not dead yet. go and pop one more cap in the splayed zombie, then back up and wait for it to stand up. repeat till it dies for good.
no zombie should take more than 10 bullets, max. 'cept for crimson heads, of course