[E. Pluribus Unum]

There is no full faith and credit concern here. Not even close.

So gay marriages executed in one state are expected to be honored by other states because of the full faith and credit clause, but gun permits aren't?

[HitmanLV]

So gay marriages executed in one state are expected to be honored by other states because of the full faith and credit clause, but gun permits aren't?

Yes, that's exactly what will happen when the legality of the DoMA is challenged.