Armor penteration
In the gun/armor race, the gun always wins. Armor may take a temporary lead, but in the end, the gun always wins. This is true with tanks, and why we don't build fortresses anymore. I would imagine that it applies to a certain extent with body armor.
Will round "x" defeat armor? Well, yes and no, depending on exactly what kind of armor you are talking about. A "rated" vest? 1/2" armor plate? the turret of an M1 tank? Just depends on exactly what you are talking about.
I recall an incident in the late 60s or early 70s, where a State patrol spent quite a bit of money on "bulletproof" vests. They would stop .38, .357, 9mm, .45, etc. Turns out that they would not stop a .22. State agency much embarrassed.
Vest technology has improved alot since then, but the idea of a "bulletproof" vest is a pipedream. There is ALWAYS something out there that will penetrate it. You can make them proof against some things, but not everything.
I disagree with those who say the subject should not be discussed at all. I think that it should not be discussed in specifics, such as "Acme vest stock#1234 penetrated by caliber xxx, barrel length xxx, bullet xxx" etc. But general discussion should be tolerated. Free speech vs public safety, where to draw the line? My opinion is the press already drew the line (and promptly jumped over it) with their (innaccurate) tirades against "cop killer bullets". This is old news, but the major result was to raise general awareness of the police wearing vests.
These same people, in the age of terrorism, go to great lengths to show everyone just where on the Golden Gate bridge to place explosives! Compared to efforts like this, I think a general discussion about vests and penetration should not be proscribed.
After all, a bullet proof vest can also be penetrated by an icepick wielded by an enthusiastic middle schooler. Or any rifle legal for deer hunting, and some that aren't. This is not news, nor is it unknown to anyone even remotly interested in the subject.