Frangible rounds will both not always stop someone and sometimes penetrate walls. What they always do, when hitting a person, is leave a wound that's much harder to heal and harder to treat.
Frangible rounds are not used in military or police agencies in any numbers because they simply don't do the job as well as conventional ammunition or they violate the Geneva Convention. The are used in many indoor ranges to allow the use of steel targets indoors, but those range owners soon find out what a mess they make of everything in the range.
Jeff
I think some clarification is in order because although sometimes "hollow points" and "jacketed hollow points (JHP)" are considered to be "frangible rounds" that is not the best definition and not the definition Jeff is using here.
"Solid" bullets
These are generally defined as bullets made from one material, typically lead. These include "wadcutters" a target ammo where the entire bullet fits into the cartridge case and "semi-wadcutters" where the all lead bullet protrudes from the case and has a flat nose. These make neat holes in targets to make scoring for competition easier.
"Jacketed bullets" These include both full-metal jacketed (FMJ) bullets and semi-jacketed bullets.
"Full Metal Jacket" (FMJ) are (typically) lead bullets encased in a copper jacket. They do not expand when they hit flesh. They are used by the military to meet Hauge Accord standards and are also used as cheap target ammo.
"Hollow points" Bullets with a cavity in the nose designed to expand upon impact in flesh. They can be all lead (HP) or have a copper jacket that covers all but the tip. These are called "Jacketed Hollow Points (JHP)". Although, in use, many times both HP's and JHP's are called "hollow points" as a generic term.
Some people do consider HP's and JHP's to be "frangible ammo" as they can break up in a target but they don't meet the strictest definition below.
"Frangible Ammo" The most common type is made for use in indoor ranges, especially when shooting steel targets. The bullets are made from sintered metal. That's essentially powdered metal reformed into a solid. When they hit a steel plate or other solid they pretty much disintergrate. While they are still dangerous, they are not designed for self defense or hunting use. This is what Jeff was referring to when he talked about "frangible ammo."
Another type are Glaser Safety Slugs. These use what is essentially multiple pellets suspended in mercury (I think?). The idea is that they will be effective against people without going through interior walls. The downside is they are extremely expensive and, guess what, they still penetrate walls.
