Chili Vega
US Veteran, Absent Comrade
High velocity self defense handgun rounds do not expand and penetrate less in building materials. They require (As mentioned above) a liquid based medium (people are mostly liquid) to expand properly. They will deform when striking 2 x 4's, sheetrock, etc, but not expand. When you reach rifle velocities in the .223 range you have a very light bullet going very fast. This causes it to break up. This is where the high velocity SD argument makes sense.
