Reality is that most Fudds are lazy tightwads who define ammo availability by what's at their LGS. They don't order ammo online. They don't look hard for ammo. And the one cartridge that's universally available for rifles is... the .30-06.
.30-06 is also available in way more Fudd guns than .30-30 because .30-30 only works in lever actions. The .30-06 works in Fuddtastic favorites like the Rem 700, Savage 110, Rem 760/7600, Rem 740/742/7400, and Browning BAR semi-auto, not the machine gun. Plus break actions like the Ruger No. 1 and NEF Handi-Turd.
Of course, there's also Fudds who do like CMP-style guns, which throws in the M1, M1903, and M1917.
Personally, though, I think that Fudd isn't established by what guns you own, but rather their simple minded cowardly mindset.