I don't really have much further to contribute that hasn't been well-covered already. Many good responses here.
Regarding ammo availability, .223/5.56 and 9mm has the highest retail volume and will be the first to be restocked -- the factories will produce more of this than other cartridges. Reloading .223 is fairly easy for a bolt action, much more so than for an autoloader. You can get by with neck resizing after the first firing in your rifle.
I suggest that early on you invest in a primer pocket swager:
https://www.midwayusa.com/product/1012920663?pid=235832
This will make using scrap military 5.56 brass much, much easier, and in times of scarcity, milsurp brass may be the most available. Also check GunBroker for deals on reconditioned Lake City brass.
That said, ex-military brass isn't always the best choice -- especially if it was fired in a SAW with headspace issues. You don't really need many reloadable cases to feed a bolt action, 200 or 300 cases will last you for years. If you can still get some new factory brass, or new ammo, that is always the best source for brass. Midway still has some in stock:
https://www.midwayusa.com/s?userSearchQuery=223+brass&userItemsPerPage=48
As far a rifle choices go, after reading the above discussion I think
I need to consider adding a midrange .233 target rifle to my safe! I currently have 3 rifles in .223/5.56, an NEF single shot, my CZ 527 beauty and my Troy pump-action AR stand-in (because California) -- none of them are set up to shoot small groups much past 100 yards, though they are all good fun to shoot.
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