So--frangibles.
First off, there are two types--the defensive frangible bullets (Glaser, MagSafe, et al) and target frangible. The difference being that the target rounds are designed pretty much exclusively to be used for shooting steel at close range; they're a sintered (powdered metal that has been treated with just enough heat to make it stick together) copper alloy that, when it hits something harder than itself--like steel--it reverts to powder. Caveat being that things like flesh, sheetrock, and other common substances are NOT harder than the bullet, and it'll just act like a FMJ.
Defensive frangible? Usually a thin-skinned copper jacket filled with smaller shot; Glaser, I think, uses #12 or #6 (blue or silver tip), Magsafe uses slightly larger (BB?--not sure if Magsafe is even made anymore, though). They tend to make very graphic, but very shallow wounds that, barring a perfect squared up shot, likely won't penetrate to vital organs. I tend to agree with (iirc) the late Col. Cooper's assessment of the rounds that "Sure, they'd be fatal--the receiver will expire several days later of peritonitis...". I also tested the Glaser rounds (blue, iirc) back when I lived in an apartment; the .357 magnum version, using a 4" GP100. Testing medium was two sheets of drywall with a 3.5" space between them. All rounds fully penetrated both sheets with absolutely no signs of fragmentation. They also shot incredibly low--4"-6" at 20 feet.
The new ARX rounds don't impress me either: tested some when they came out under Ruger's banner--the .380 load. Out of my Sphynx AT at 10 feet, the rounds went clean through a 1 gallon water jug, through two sheets of spaced sheetrock, and buried themselves several feet in hard dirt (deeper than a cleaning rod). So much for "frangible", there.
But--this is just in regards to handguns. Rifles are a whole 'nother story.
Rifles have the serious velocity to make frangible act they way they should; and by frangible, I'm referring to "varmint rounds" such as the Nosler Ballistic Tip (NBT), Hornady V-Max, Winchester Ballistic Silvertip...etc. These are devastating in squishy stuff, but will come apart FAST when they hit much anything else--such as sheetrock. Doing some real life testing in a house that was going to be torn down, we found that out of a 12.5" or longer barrel, a .223 55gr NBT would go through one interior wall, but be stopped in the next wall, interior or exterior. This is pretty darn good. Out of a 20" barrel, it would get through an interior wall and would leave fragments in the next, but wouldn't get through an exterior wall.
Note that it still goes through walls, though. Any round suitable for self defense will...TANSTAAFL.
TL/DR version: good in rifles, bad in handguns. Know the difference between target frangible and varmint rounds.
www.usconcealedcarry.com
) at the FBI and the like actually implements modern frangibles as their chosen duty cartridges.
