Below is an example of the effects of bullet construction materials and powder loads to an automobile fender. The plain lead bullets will deform (flatten) when they encounter the resistant target.
Jacketed bullets tend to keep their shape longer than unclad or hollow point bullets.
As the plain lead (or hollow point bullet) deforms, it increases in diameter and transfers energy to the metal to dent (inward) resulting in a crater. This crater is highlighted by the paint which is broken
from its bond to the underlying metal. The measured of the hole created by this deforemed bullet (flattened) will be greater than the nominal caliber (diameter) of the bullet prior to impact.
A general rule of thumb is: “The greater the crater, the greater the diameter of the bullet hole will be than the original nominal caliber.
For example: (with lead bullets) .22 caliber may leave a nearly 30 caliber hole; a .38 caliber, 9mm, or .357 (all same nominal caliber) may leave nearly a .45 caliber hole. A .45 (44) caliber
bullet may leave a hole greater than half an inch... or more in diameter.
Definitions for picture at left:
.22 caliber Long Rifle (LR)
Lubaloy is simply a paint like coating on a lead bullet.
