Don't underestimate the .243. Growing up, my Dad killed many, many moose with a Ruger .243 - he preferred it to all other rifles when hunting moose... it's a wickedly fast round and extremely accurate. More than once I witnessed him crank the scope up to 9 and one-shot-one-kill the moose that was just a speck on the horizon. He would break it's neck every time with his shot in order to minimize meat damage from shooting it in the front quarters.

A .270 is another extremely fast and accurate round, but it's going to have more recoil.

My two cents, Perianne, a .243 would be fine. Ideally against humans you'd want a larger caliber round, but if you're comfortable with the kick from a .243 and it's about your maximum, then I'd say use it. If it can break the neck of a moose, it'll do everything you need against a human.

I don't know how much experience you have with firearms, but if you're new... practice, practice, practice.

A good SHTF pistol should be in order, as well. A 9mm automatic pistol doesn't have much kick and it's very effective against humans - and in close quarters, that's what you're going to want to have instead of your bolt action rifle. My step sister is an avid shooter and practices with her 9mm all the time... she's only about 5' 4" or so.