an excerpt from Max Brook's book "Zombie survival guide", great book
8. .22-CALIBER RIMFIRE WEAPONS
These weapons (rifle or pistol) fire a round no wider than a few millimeters
and no longer than an inch. In normal circumstances it is usually relegated to
practice, competition, or the hunting of small game. In an attack by the
undead, however, the diminutive .22 rimfire stands proudly alongside its
heavier cousins. The small size of its rounds allows you to carry three times
as much ammunition. This also makes the weapon itself lighter, a godsend on
long treks through ghoulinfested territory. The ammunition is also easy to
manufacture and plentiful throughout the country. No shop that sells any kind
of ammunition would fail to stock .22 rimfire. Two disadvantages present
themselves, however, when the use of a .22 is considered. The small round
has zero stopping power. People (including former President Reagan) have
been shot with .22s and not even realized it until later. A ghoul taking a round
to the chest would not even be slowed, let alone stopped, by this puny
projectile. Another problem is the lack of skull penetration at longer ranges.
With a .22, you might have to get a little too close for comfort, a fact that
could increase stress and degrade the odds of a kill. By the same token, the
lack of power in a round fired by a .22 has been called a blessing in disguise.
Without the force to punch through the back of a zombie’s skull, .22 bullets
have been known to ricochet inside the brain case, doing as much damage as
any .45. So when it comes time to arm yourself against a looming zombie
menace, do not discount the small, almost toylike nature of this nimble,
efficient firearm.