Lake City makes ammunition for the US military. NOT for civilian consumption (except ammo that is surplused out).
What a wonderful thing to do... Produce ammo that would go into the Government supply train with a "drop dead" date.
As far as actually doing something like this, no, it's not as easy as one would think.
Given the lot to lot variations in gunpowder already, even when the manufacturers use the same materials, it's very very doubtful if they could accurately make a cartridge that would expire after a definitive amount of time, say 5 years.
What would happen if it was stored in a cool, dry place? Would it last longer then if it were stored in a hot, damp location?
What would happen to the life span of the ammo under transportation to a combat zone half way around the world, and storage in a forward ammo dump where days might be blazing and nights might be freezing?
As others have said, these rumors, and many like them (like a secret Gov't funded organization is using stimulus money to buy up all the primers to keep ammo supplies low
) are just that - rumors.
They're to be laughed at, with suitable amounts of finger pointing and ridicule.