Remember bullets cause damage due to punching hole in things, In living creatures holes in organs and blood loss is bad. Structural damage is secondary against live targets but torn ligaments and shattered bones would have more of an effect on zombies, So Bleatles microwave actually has a use as a weapon for once,for the 1st zombie the 50 others will just charge in and devour him. But the Chainsaw is where its at in modern anti-zombie warfare.
See D&D and Rifts does learn ya stuff