There are a lot of reasons why ammo can be "downchecked" and scrapped or sold as surplus. But, by far the most common one is simply age.
Many militaries today (probably most?) have age limits on ammo. Not because the ammo has deteriorated, but because they have determined that after a certain amount of time, it
could.
Think of it as a "best used by" date on any chemical product you see. (not food
) In the US, every product with a chemical component has some "expiration date" given by the manufacturer. It may be an actual date, or it may be a specified time from the date of manufacture, after which, the maker no longer officially stands behind the product.
Unofficially they will usually tell you that if the product looks, smells, and acts good, despite the age, then it probably is still good, but officially, past a certain date, they will no longer guarantee the product is good. Paints, solvents. glues, cleaners, fuel, all kinds of things, including gunpowder and primers.
We all know properly made ammo lasts a long time in proper storage. But even in proper storage, there is a determined shelf life, after which, while the stuff you have probably is still good, it's no longer trusted to be good.
IF, for example the shelf life is 20 years, the military may scrap it at 10 years, just to ensure its quality. Small arms ammo is cheap, and cheaply replaced in the scheme of military expenditures.
Now, why "reclaimed" primers? why not just sell the surplus ammo intact?? Some places have (relatively new) laws / rules about selling surplus ammo. Europe used to be a major source, but in the past couple decades they have stopped, due to political pressure to reduce "international arms trafficking".
Some places won't allow surplus ammo to be sold but will allow recovered components to be sold.
Bullets rarely degrade. Cases, powder, and primers are another matter. And the big problem with that is when it is "reclaimed" and sold to a vendor, its known where it came from. After that generally its not. And the end user purchaser (you or I) almost never gets the actual history.
You never know what you're getting or how well it will work. And there's no known maker you can contact about problems.
As an example, about a decade ago a friend bought 500rns of "surplus" 7.62 NATO ammo. And took delivery sight unseen. Said it was the only time he'd ever just picked up ammo without looking at at least some of it, first.
Stuff came packed loose in a crumbling plastic bag inside a box, and there was a significant amount of sand in it as well. 99-02 headstamps, ammo was dingy but not visibly corroded.
Tested 100 rounds. 11 did not fire at all. 17 of the fired cases cracked. Every one that fired hit the 200m gong just fine and cases seemed ok. Pulldown of the dud rounds showed deteriorated powder (discolored, clumped, stuck to base of bullet, etc.)
We pulled down the rest salvaged the bullets and tossed the brass & powder. Based just on the age, that ammo should have been fine. It wasn't.
Now, today, with the high demand for primers during this shortage, someone might just be taking crap ammo, "Pneumatically reclaiming" the primers and selling them for a LARGE profit.
You and I aren't going to know anything is wrong until we get a click when we expect a bang. For me, its not worth the risk if the ammo I loaded with them needs to be used for something serious, and not worth the aggravation if its used for recreation, and fails to fire.
And, with an unknown and un-knowable history, its absolutely not worth the price of new, verifiable quality primers.
