Originally Posted by Andrew Wiggin
Theoretically, the fastest and hardest bullet has the best chance. For example, a 135 gr at 1,600+ fps. While a IIIA would almost certainly stop that, a IIA might not.
9x25mm Dillon would give you a way better chance of penetrating soft armor but your best option with a hand gun is going to be training for failure to stop. There are many reasons for which one or more hits to the chest might not stop a threat and all of them are remedied by a hit to the CNS....
....except for unstoppable robot killers from the future. The only thing that stops them is a phased plasma rifle in the 40 watt range.
This. 9x25 = AP happiness
Velocity is the key to penetrating hard body armor. for soft body armor using a pistol, you need a very hard very pointy projectile to push aside the fabric threads. I imagine that there a ration of velocity to the diameter of the projectile, with the smaller the projectile the lower the velocity required to penetrate.
I imagine a brass inverted cone would do the trick really nicely, but thats well into the realm of custom lathe work.
Such a projectile made for a pistol would also be very illegal under federal law for most people.
Bottom line if you are going to be in a fight with armored personnel, bring a rifle and shoot often and early.