wiped down all of the ammo
It's very hard to make a magazine that won't rattle, ever, because the ammo isn't all exactly the same. You're putting 13 rounds of ammo in there, so you're stacking tolerances x 13.I own a gen 4 Glock 23. It came with 3 mags, all function perfectly. One of them makes a rattling noise ONLY when it is fully loaded with 13 rounds of ammo, the other 2 do not do this. Is that anything to be worried about?