I have the .40 that's loose in a can. I don't see where it damages it. It's not being tossed around or moved frequently.
I find this method of storage a total pain in the rear. When I go to load mags, it's just one little extra step of fumbling with each round to orient it to load. When you pick it out of a box, you're always grabbing the same part.
Just my .02.
Moosie