I wonder at what point the ammo would be gone, and the means of reloading ammo gone. I'm guessing within 50 years virtually all ammunition, except what has been hidden and forgotten about will be gone and the only survivors will be those who know how to manufacture gunpowder and extract lead from items.
I'd say if a major event happened now, must of us would be dead in 50 years. Buy it cheap and stack it deep