For straight up survival in the woods/rural areas that I occupy, where I wasn't concerned about self defense I'd probably say my NEF/AAC Handi-Rifle in .300 Blackout backed up with a handgun suitable for small game (Kit Gun/4.5" Woodsman/SP101 in .327 Mag, 2-5" Model 10, etc). 50 or 60 rds of .300 Blk would do you for quite awhile, along with a 50-100 rds for the secondary, and the outfit could be pressed in to defensive usage if necessary.
I do have an AR carbine in .300 Blk, but find the single shot so much more comfortable to carry that unless any kind of conflict might be anticipated, the single shot gets the nod. I have a Leupold FX-II 2.5x on it and it's more than suitable out to a couple hundred yards with handloaded 125 gr Ballistic Tips and a healthy (above book level) charge of H110/W296...
For me it is a gun I already own left to my by my dad. It is a Savage model 24 rifle over shotgun. It's a 22lr on top and a 12 gauge on the bottom. I have the 12 gauge Chaippa 12 gauge inserts also. This converts the 12 gauge to another caliber by inserting a metal adapter that holds a different caliber. You can then shoot .22 lr, .380, .45LC/.410, 20 gauge, .45acp, .38/.357, .44mag, 9mm and .40. More than enough flexibility for me.
If money was no issue, I’d have a KAC M110. 308 so good for pretty well any game in my part of the country and can also be used for defensive scenarios. With an optic swap and a collapsible stock it would be even better