The thought train goes something like this...
The prosecutor at your trial will make your self defense look pre-meditated and portray you as a blood thirsty killer that planned to harm any available thug with deadly hi-velocity hand loaded ammo.

Now a smart lawyer can probably neutralize that portrayal but it may still be presented and will constitute a wild card in some jurors minds. If on the other hand, you were using the same factory stuff your local police dept uses, who could question that?

I'm not a lawyer so this is just my opinion on the subject.