Just pay attention to the vendors and read thru the reviews. Look out for reviews that sound just alike / similar and have been posted very closely together. I check ammoseek routinely checking for availability and when my preferred ammo pops up in several spots then I start looking to stock up.
The current market and economic conditions have brought out way more scummy sellers than usual.
Be sure to do a search of potential seller's reviews.
If someone has ammo no one else has at a lower price, beware.