Frangible ammo is a type of bullet that is designed to break into tiny fragments upon impact with a hard surface, such as a steel plate or brick wall. The fragments are slowed more rapidly by air resistance and are less likely to cause injury or damage to other objects. Frangible bullets are made of composite materials that are pressed together with adhesives or formed under high pressure into a "solid" bullet shape. They are sometimes known as Advanced Energy Transfer rounds or AETs.

Frangible ammo is used for a variety of purposes, including:

• Training: Frangible bullets offer improved safety for specialized combat simulation training, which involves one or more shooters engaging multiple steel targets from various directions while moving through a 360-degree range, due to the decreased risk of ricochet, overpenetration, as well as decreasing lead exposure.

• Close-quarters combat and law enforcement: Frangible ammunition is used by law enforcement for close-quarters situations, where officers and military personnel can reduce the chances of overpenetration in walls and targets by using frangible ammo.

• Environmental safety: Frangible ammo is lighter than equivalent lead core FMJ ammunition, making it safer for bystanders and the shooter. Military and law enforcement agencies use frangible ammo to increase safety for bystanders and the shooter.

Frangible ammo is not without its downsides. For example, because it doesn’t penetrate well, frangible ammo is not the ammo of choice for most self-defense scenarios that are unpredictable by their very nature. Additionally, frangible ammo is made of a softer bullet, so there is an increased chance of jamming in the rifle or other issues.