Alot of “preppers” want to give me hell for recommending a .22LR, but the ammo is good for barter, cheap, easy, reliable, and dont the the round fool you, you can easily kill a man or deer with it with proper shot placement.
Have killed many (approx 3-5 a year) hogs with a 22lr. X between the eyes and ears and down they go with nairy a problem.
I’m down with your recommendation... as a starting point