This rumor started back in the Clinton administration, when the Dims were pushing all kinds of gun control schemes.
One was to put a "taggant" in gun powder that would make it possible to trace the maker of the powder and to the company that loaded the ammo and even the batch. This was touted as making it possible to trace ammo used in crimes to a buyer.
When it was learned that this could make the ammo unsafe and the military and police flatly refused to even consider it in their ammo, cooler heads prevailed and the idea was dropped.
Some Dim politician asked the question if it might instead be possible to make ammo that would expire and stop working in a certain amount of time, and that too was dropped when it was learned that it wasn't possible.
Of course the gun shop and internet rumor mill went into overdrive claiming this was GOING to be done.
After a time most people dropped the rumor, but it still pops up from time to time.