Quite simply, if you make the decision that a handgun is a part of your Zombie Apocalypse planning, then it is necessary to actually practice with the type of weapon that you intend on using. Ideally, find a weapon that works for you (ranges with rental weapons are ideal for getting a feel for this) in a decent common caliber ( .45 ACP, .40 S&W, 9mm, .357 Mag, etc.) , and then stick with it. Use reduced-scale zombie targets to better understand the difficulty of that “head shot”. Then- practice, practice, practice.