I came across this while following other threads about ammo.
http://www.firearmstactical.com/tacticalbriefs/2006/04/main.htmhere's a quote from that article:
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According to Steve Johnson, Hornady Marketing Communications Manager, the Critical Defense line of handgun ammunition:
"...is not designed to shoot through glass, is not designed to shoot through a car door, and is not designed to shoot through a wall. If you have to shoot through something like that in a personal defense situation you're probably going to jail."
-- NRA's American Guardian TV
Thus if you carry a concealed handgun for personal defense and need to shoot from the inside of your car, through glass or sheetmetal, then you cannot rely on Hornady Critical Defense handgun ammo to perform. If you're stopped at the side of the road changing a flat tire and you're attacked, you cannot rely on Hornady Critical Defense handgun ammo to shoot through glass and sheetmetal, if that's what it takes to stop the attack.
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This sounds to me, a better reason not to use it, rather than hard primers.