Also, when you and the zombie are at slightly different elevations and you aim up or down to its level, you have a higher chance of scoring a headshot. Samurai edge gets more headshots than the handgun.
[header] How to prevent crimson heads in resident evil [title] Decapitate it. [substeps] Shotgun: to blow off its head, wait until the zombie gets really close to you, and then aim up and fire. Handgun/samurai edge: after two well placed shots to its upper chest, you might get lucky and blow off its head on the third shot.