I've never run out of .280 ammunition and needed to buy more on a hunting trip. But I can see how that could be a problem under certain circumstances. If that's an important consideration, then it would make sense to confine yourself to popular calibers like .223, .22-250, .243, .270, 7mm Rem Mag, .30-30, .308, 30-06, .300 Win Mag and possibly .338 Win Mag when travelling in North America.
Or, you could always take a backup rifle in 30-06. That's what I do.
If I'm driving to the hunt I always take a backup rifle. If I'm flying that increases the baggage costs but may still be worth it depending on the situation.
