Again, I would to ask for clarification. In the instance that you referenced, what was the actual charge (or charges) based on the weapon itself that the person was convicted on?

If the shooting is justified and you can demonstrate that in court, the type of weapon (as long as its a lawful weapon to possess and use) is of no consequence to the posecution of the case.

If you're talking about a switch-blade or a sawed off shotgun, or a handgun with the serial number scratched off, or some ammo you made yourself by pouring mercury into the hollow point... or if you've demonstrated a history of poor decisions like pipe-bomb making, etc., then you might have an awful time with your defense in killing someone.

But if you're attacked in your home and you shoot and kill a guy who had the intent, means and opportunity to kill you or do great bodily harm to you -- and the gun and ammunition you used were legal to possess and use -- and you dont have a history of nutty activity related to weapons -- then unless you've got a completely retarded attorney, you arent going to have to worry about spending time in prison just because you chose a .44mag rather than a 9mm.

I've personally been a party to a handful of court cases involving shootings, and I've reviewed testimony and evidence in quite a few others... and I have spent a lot of time in courtrooms on non-shooting weapons related cases, and I have never personally seen the type of weapon become an issue unless it was an illegal weapon or unless the individual had some questionable weapons related history that was relevant.

And in cases where this is purported to be the case, I would venture that there are circumstances or evidence which cause complications beyond the simple choice of caliber or ammuniton.