回复：如何算合法用枪自卫？

If you are at your own home, when there is an intruder with deadly weapon or you reasonably believe he possessed a deadly weapon, you can use the same level of deadly force to pretect your self and your family, but not your property. The key is the reasonableness. If your action is reasonable to most lay person, then you will be fine. But you should always try to avoid to use deadly force whenever you can.

Look at the State v. Alexadra Pring-wilson case recently. He used knife to defend himself in a fight (he said he was self defense) and accidently killed that guy. He is guilty of involuntary manslaughter and sentence 6-8 years in prison.