I got an AR-15 (Bushmaster carbine) specifically because of the compatibility of ammo and magazines. I got a Springfield M1A next because of quality and because the military still uses 7.62mm and to some extent, M-14s.
As far as I'm concerned, a "gun ban scenario" is pretty much the same thing as a SHTF scenario.
If it's time to bury them, it's time to dig them up.
Quote of the decade, my friend :)