The thing to beware of is the less-than-total loss.
Your average homeowners and inland marine policy claims department does not understand fine art. They will argue you've suffered no covered loss under typical conditions. Let me give you examples:
1.) You have a fire. Your guns are in a safe. They smell and they are sooty, they want to pay $200 to have them fumigated. Um...no. Total loss. The heat has annealed them. The wood has been dried out due to excessive heat. The originality has been lost.
2.) Your double rifle was violently dropped by UPS, FedEx, or an airline. The rib has come loose. The cost to repair includes 1.) Re-regulation plus cost of ammo. 2.) Reblacking the barrels after braising the ribs. 3.) Sending it to London for reproof, all charges, plus cost of import/export licenses, plus a British gunsmith to process all the work, plus insurance coverage to-and-fro. 4.) Loss of value due to alteration and reproof.
3.) Your original custom or best gun has the stock cracked. 1.) Cost of new wood, $4000-$8000, 2.) plus 2 year wait to have it inletted and fitted for $4000-$12,000, 3.) Plus shipping/insurance/customs to process import/export, 4.) Plus loss of value now having a replacement stock.
Good luck trying to persuade some general purpose claims adjuster from your Allstate/Progressive/State Farm/Farmers agency that after spending $20,000 to repair your $15,000 gun, the gun is now worth $8000. Thus a total loss since the cost to cure and the loss in residual value exceeds the worth of the firearm.