Home Owners Insurance
Traditionally firearms are covered under the same coverage as all personal property. Check your policy to see what your limits are for personal property. In the case of a fire this coverage is the max payout you can receive if all your property is lost. If you feel that max payout is too low you may want to make some adjustments to your policy. Also confirm which “perils” are covered. Theft and fire and generally included “perils” but loss or breakage are generally not included in the coverage.
In addition, one should also be sure to have a complete inventory of one's property including firearms. If you can't prove to the insurance company that you owned inventory to begin with they won't reimburse you. The best way to create the inventory is to use a video camera. Clearly show each firearm and all the accessories and safes in the house. Store the video on a disc or USB drive with a family member or in a safe deposit box. Keeping it in the house won't help you much when the house burns down and your inventory is also lost.
NRA Membership Coverage
If you are a member of the NRA your membership also comes with $2,500 of ArmsCare coverage. This plan covers insured firearms, air guns, bows and arrows against theft, accidental loss, and damage. This coverage is not automatic. Once your membership is live you need to activate the insurance coverage. Visit this NRA membership overview page and click on the link to activate.
If you aren't a member you can join the NRA and get $10 off your first year's membership here.