I have never had a NICS background check take more than 5 minutes. Never.
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I have had a background check take more than 3 days and the dealer let me have it after that time period without the check being complete as the law allows. Fall of 2001, some back water pawn shop in Montana buying an 870 after my principle gun failed on the trip. I never shot the 870 that trip but instead and old straight stocked G grade Lefever which was too short for me and had too much drop. Still a great trip though and that was one hell of a bird dog.