It's pretty easy to find ammo for the firearms you own. I agree with those who say keep what you can. In terms of a .243 Win being desirable, the local Bass Pro had a new-on-the-shelf M70 Ultimate Shadow .243 Win for $399. When I asked why, the worker commented, "We've had it for a few years (made in 2010), and nobody wants a .243! It's the last one we have..." Well, I just happened to want a .243 Win at that dandy price! JMHO, keep 'em if you got 'em.
Geno
Geno