Started before that.
Federal Match Large Rifle (210M) primers were scarce for at least a year before that.
The guns and ammo rush is a social phenomenon, not merely a market blip.
It makes an interesting topic of study as to when it began, and what the drivers are of what has become a social movement, that the Dems want to portray as "fear of a ban."
There is a lot more going on than just that.