I have a few questions for Sethsquatch.
What type of area do you live in? urban, suburban, rural
How long are you expecting to have to hold out? 2 weeks, 1 month, 6 months, 1 year
Are you looking to stay in place or try to leave for somewhere out of the affected area?
Is this carbine for home/self defense or for hunting as well?
In the meantime this is what I've noticed at our local Wally World when it comes to ammo.
When the ammo shortage was at it's peak I could still find tons of 12 gage bird and buckshot.
All pistol,revolver calibers were long gone including .22lr!
The only rifle/carbine ammo I could find was 30 Carbine and 7.62x39. (A box or two fo 30-30 could be found sporatically. All others were MIA.)
Now that the shortage is slowly, crawling back to somewhat normal, this is what I find.
You can find almost all caliber ammo at the gun stores, but at W.W. you can only find
40S&W, .38 special, .223, .308, 30-30, 7.62x39, and a smattering of 30-06
This, to me, points out the obvious. Common ammo calibers are owned by the majority of people and those calibers are the hardest to find in a crisis or during a panic of an upcoming crisis.
And I don't recall anyone offering to trade off any of their ammo during the shortage either.
So my recommendation to you is to put to paper what your Katrina situation means to you; What caliber of ammo you can find and afford to buy; And if you plan on lugging all that ammo around with you or use it mainly at your homestead. Then go from there.