Stupidest thing I ever did was to make up a bunch of .38 Special wadcutter loads, then leave the top of the plastic box off.
Later, I'm spraying WD-40 on a firearm and noticed that the spray is landing all over the backs of my .38 ammo, in the box.
Oh well ... no harm done. So I thought!
Darned WD-40 crept in around the primers, over the space of a few days, and deadened about half of the primers.
It's not easy pulling a hard-crimped wadcutter bullet. I pounded the inertia hammer and still couldn't get most of them pulled.
Ended up deep-sixing them at Badger Lake near Cheney, Washington, next time I went fishing.
Badger's a deep, narrow lake. Never seen a scuba diver there, so I figured they'd never be found or recovered. That was 25 years ago or so. They're probably six inches under the mud by now.
I haven't used WD-40 since. Not only will it deaden primers, it turns to a hard, sticky varnish over time. Terrible stuff. It will gum up car locks, padlocks and anything else you use it on.
For firearms I use any of the light oils. For locks I use silicone spray.