I was looking for 16ga ammo once, and was told the store didn't have it (fine, happens all the time, even before the shortage). The clerk went on from Earth to planet ***.
"You know, you can't use 16 for hunting" (it was close to bird season, good and accurate guess to my intended use)
"What????"
"You can only use 12ga or smaller"
"What about 20ga?" (not bothering to make this conversation longer and more confused with facts about how gauge is measured)
"That's ok, but I think its because it's metric"
What can you say to this? Talking about guns and legalities sometimes is like being the only sober person at the party. "You can't work on your own firearms", "Shortening a shotgun barrel (to 19") is making a sawn off, and is a federal crime", "they make guns now to go through airport detectors", "a .50 can bring down the space shuttle at launch" and anything else ever penned by "Gunkid" (can't believe I'm the first to reference the troll of trolls)