I, too, have no heirs. Everything I have that's related to guns (a LOT) will go to Amoskeag Auctions, a big national-level auction house that is local and will sell not only the guns, but everything else firearms-related, too. And, at least based on what I have to pay for everything I buy there, they should get good money for it. They are in Manchester, so they can easily come get it all. And, unlike RIAC, they don't do that bogus "bundling" of any guns worth less than about $1000-1500.
All the proceeds were to go to NRA, but I have been DONE with the NRA and LaPierre since the Big Bumpstock Capitulation, so now it will all go to GOA. Given the efforts by GOA, SAF, and FPC lately regarding the "pistol brace fiasco" (while NRA did absolutely nothing) and their lawsuits to stop it, I may edit that so all 3 share in the proceeds. I also used to have all my Amazon "Smile" proceeds go to NRA, but that all got changed to GOA back in the bumpstock days.
All this is spelled out in detail for my wife if I go first or my executor if I go last. ITMT, I continue to collect
I have a couple family heirloom guns that MAY go to a niece's children or a cousin's grandchildren, but only if I decide they will keep and appreciate them.