I'm against using spent cartridges for dry fire especially "for storage" Here's why:
AND NOW YET ANOTHER ANNOYING story from the old days
Dad had a couple of semi auto rifles Remington? I think? has the magazine in the butt. Anyhow, one of them had a fired round in the chamber and I was fiddlin' around and could NOT get it out of there. And I fiddled and diddled and tiddled and you know. And, about the 5th time I fiddled, and dry fired the thing IT WENT OFF into the floor of my upstairs bedroom. It turned out to be a short, and did not go through the ceiling below. BUT GOD DAMN!!!! I had dry fired the thing several times, and it "looked" like it obviously had been FIRED!!!