No commonly-affordable large safe is entirely fireproof, much less any gun safe, but they can be made fire-resistant - for a certain length of time/temperature.
Most quality gun safes (NOT steel gun cabinets) are UL-rated for 1200-degrees for about 30 mins +/-, which is usually enough for gun protection.
Additional internal insulation boards can be added for those so minded.
If your house burns down, believe me, you'll have a lot more things to be concerned about, than some guns.
Most of the $$$$ paid for in a "name" brand gunsafes are in the wall/door & locking bolt thickness, number of locking bolts, door hinge construction, and lock quality.
Many different safes are actually built by the same company to different specs & brand stamped - just like Savage/Steven made rifles for Sears.
I would look at an UL fire-rated safe by a decent maker like Cannon/whatever, with enough capacity for 2x what I thought I might need, and heavy enough (empty) to deter carry-away - then look to a discount online dealer ( I used Sam's Club), for the best price.
I bought a 600lb, 22-gun, Cannon/Winchester safe for $700, which (with careful insertion) holds 30 long guns, 25 handguns, several scopes, plus jewelery, bullion and important family papers (deeds/insurance/birth cert/passports/etc).
I try not to secure dead airspace in my gunsafe, so it gets packed.
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