Maybe stanne can give you other cites. I have read these citations in the catechism:
2263-2266 in the “legitimate self-defense” section.
Those don’t refer to 2nd Amendment directly, but the language is precise, clear and not only refers to the right to defend yourself, but the grave obligation to defend others you are responsible for.
It’s good to see the truth get out what the Catholic church actuall teaches. :)