What is the characteristic of armor-piercing ammunition?

Armor-piercing ammunition is specifically designed to penetrate armor and other barriers effectively. The correct choice highlights that this type of ammunition is typically made from dense materials like solid carbon or tungsten steel, which grant it the ability to penetrate hard surfaces that regular ammunition cannot. This characteristic is essential for its intended use, as traditional bullets often deform or become ineffective when striking a hard target.

In contrast, minimal harm does not describe armor-piercing ammunition since its purpose is to maximize penetration rather than minimize damage. While it's true that the cost of armor-piercing rounds can be higher due to the materials used and the manufacturing processes involved, this is not the defining characteristic of such ammunition. Additionally, armor-piercing rounds are not commonly used for general training; their unique design is specifically suited for offensive or tactical applications rather than everyday practice scenarios.