I wouldn't want to wear a IIA vest and get shot with a .45ACP
these vest are rated for 9x19mm and .40 S&W. While a .45ACP may not penetrate it, you would sustain some serious blunt force trauma from it.
7.62x25mm will pentrate IIA like needle through warm butter.
As I am sure, 10mm, .38 SUPER, .45 SUPER, .460 Rowland, .440 Corbon would also penetrate it.
But quite honestly a lot of calibers with and bullet types can penetrate body armor. A hard ceramic plate is the best bet.
http://bulletproofme.com/Ballistic_Protection_Levels
Brother In Arms