When talking self-defense ammo, all manufacturers claim effective expansion. Various test show these claims are not always accurate. However, when it comes to .45 ACP I'll be the first to claim that expansion doesn't really matter.

From at size comparison, a 9mm must expand 27% to create the same entry hole as a 45 ACP. Likewise, a .40 caliber must expand 13% which is better than a 9mm but still doesn't match the .45 ACP. So assuming that a .45 ACP does not expand at all (chances low) it still creates a very large hole. Any expansion is just a bonus!

To be fair, the wound cavities created by these projectiles will be different based on bullet weight and velocity. However, the simple fact is that an entry wound from a .45 ACP is going to bleed; and FAST!

Not everyone chooses to carry a .45 ACP for a defense, but you can't deny the advantages of a large bullet.