Shotgun slugs can produce significant injury, because of the slug's size and mass. Bullet design is important in wounding potential.
For steel targets, the concern is to provide enough force to knock over the target while minimizing the damage to the target. Such bullets are typically made of a metal other than lead, such as copper powder compacted into a bullet shape, as diagrammed below:.
These weapons are easily concealed but hard to aim accurately, especially in crime scenes. The hollow point peels back into eight or nine connected pieces causing it to expand the damaged area.
Terminal ballistics - Wikipedia
This increases the effective surface area, as rounded bullets can allow tissues to flow around the edges.
The purpose of firing a large calibre projectile is not always the same.
At close range less than 4 feet an entrance wound would be about 1 inch diameter, and the wound cavity would contain wadding.