I was bored at work, so here's some data to consider:
For defensive handgun cartridges, the IWBA testing protocol recommends a penetration depth of 12.5" - 14". The FBI protocol recommends 12" - 18".
If you're starting to visualize this in relation to a human body, keep in mind that the skin on the entry side is equivalent to ~2" of gelatin, and the skin on the exit side is equivalent to ~4". If you have an attacker holding a weapon up, and you shoot through their arm
like so, it takes 10" of penetration to even reach the torso (2" for the enrty skin + 4"
through the arm at an angle + 4" for the exit skin = 10".)
That being said, let's look at some test results for frangible rounds:
Glasers: Pre-fragmented round.
Says right on their websight that
Glaser Blue penetrates five to seven inches in International Ballistic Wound Association protocol testing, while silver penetrates eight to ten inches in the IWBA testing protocol.
This link lists glasers as having 8" (blue) and 9" (silver) out of a 357SIG.
That fails to meet the 12" minimum for either FBI or IWBA protocols, and what is penetrating is tiny, tiny bird shot.
Rounds are over $3 each.
MagSafe: Pre-fragmented round.
Their website makes an unsupported claim of 10" - 13". The
picture on the front page does not look like nearly that much penetration.
This link and
this link both list magsafe penetration as 11.3", again from a 357SIG.
Not bad for a prefragmented round, but still less than 12".
Magsafe makes mention of both the Strabourg tests and Marshall / Sanow data in promoting their product, which I personally find a little questionable.
They also mention "hundreds" of gelatin shots, but offer up no actual test data from those.
And again, what is penetrating is tiny birdshot.
Rounds are about $2 each.
Corbon Pow'R Ball: JHP
Not really a frangible round at all. The Pow'R Ball is a jacketed hollow point with a polymer ball in the point to a) give it a round nose profile for reliable feeding, and b) keep the hollow point from getting clogged.
Test results seem ok from what I've seen, though not great.
This one actually shows some pretty poor results.
I had heard of some possible QC problems with Corbon, but that was over 2 years ago, may not be an issue now.
Rounds cost about $0.80 each.
Extreme Shock: Frangible round.
I have trouble even looking at these guys seriously because of the picture on their home page. I mean, if that doesn't scream "Mall Ninja!" I don't know what does.
Anyway, their description of the "Air Freedom Round" says
An AFR round has completely dumped its entire energy in the first 7", completely disintigrating the ballistic gelatin
7" is inadequate penetration for getting to anything vital. Thier ammo also seems to be designed around the unproven "energy tranfer" theory, and the misconception that gelatin torn by temporary cavity translates to tissue damage (it doesn't).
Rounds cost $2 to 3$ each.
International: Frangible round.
Lists the primary benefits of frangible as it being non-toxic (no lead) and reduced riccochet risk for close quarters training. They do make a duty round, but I find their test results interesting:
cal...............wt.........................................pen...........retained wt.
9mm Luger....100gr...Bare Gelatin...................15.00 in.....51.0 grains
9mm Luger....100gr...Denim, T-Shirt, Flannel....15.25 in.....52.5 grains
9mm Luger....100gr...Drywall, Light Clothing.....12.25 in.....48.5 grains
The terminal performance after penetrating drywall is almost as good as in bare gelatin. And it still meets the FBI minimum for penetration. So that essentially means that your neighbors are no safer than the guy you are shooting. Although only 50% weight retention is pretty poor compared to hunting or standard jhp rounds.
No info on price.
Compare these with, say, Speer
Gold Dots which can be had for about $0.65 per round or less.
Any of the frangible or gimmick-type rounds
could work. If that's what you want to use for defense in your apartment, then feel free. But realize that you are giving up terminal performance in exchange for over-penetration concerns. There is no magic bullet.