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I only ever purchased 2 rifles from a store, and I am certain (despite my ageing memory) that I was not asked for an address by the store.

Thus building a record of what firearms are at which address....IE an informal registration. I would politely decline to give them such info unless legally required.

Did you provide those details to GC, or just present FAL as required?
If it was the latter, then yes, this is potentially a biggy imho.