Assuming I use the AR15, and assuming I don't want to use 5,56, I would go with 7.62x39 as a reasonable caliber. I have about 5000 of those little pills. They are still fairly easy to find. They Are not much heavier. I can always have a friend with an AK47 come along and still be single caliber. Make the AR a pistol, and you will have reduced the weight quite a bit as well.
Lots of good thoughts from all of you. And lots of take aways.
Being in my 60s with a wife who wouldn't be able to do the cross country running, I would most likely stand my ground. Fortunately, I'm in a community that would, most likely, band together.
Truth is, you're more likely to survive with larger numbers working together.
While I love the idea of "running through the jungle with my M16", I'm no longer that lean, mean, fighting machine that I was 40 years ago.
Having said that, defending my home, family, and friends is a different story.
Here i would have my choice of rounds and weapons. I have the high ground, sufficient open area, space, reinforcements, and the armory to back it up.
Real life may not allow the bug out scenario. But you can still do what you have to.