What kind of stupid question, a gun can't act on its own.

As for the 2nd Amendment, it comes from a time where guns for self protection were crucial for the survival of the settlers as they lived far apart from each other and there were many robbers and Native Americans that were at war with the settlers (who can blame them though).
Moreover, the 2nd Amendment goes back to John Locke's State of Nature in which there were no rights defined but natural rights which involved self-protection and protection of life, property, and liberty, but going deeper into that would go too far.