But you'll notice that these rounds have very long stand-offs. A 12 inch standoff isn't going to be too practical in a pistol, or rifle for that matter. All HEAT rounds require a certain amount of standoff, which is proportional to the diameter of the warhead and the velocity of the projectile. The faster you go, the longer the standoff.
The RPG-7 travels at something likle 150m/s and still requies about six inches of standoff.