Link for you- Gun Safes, Fort Knox: Americas Best Made Gun Safes, Hand Gun, Fireproof, Home and Vault Doors See the section on fire rating.
Standard is how long a safe can keep the internal temp below 350 when in a fire. BTW, that is accomplished by a combination of the mass of metal, a door seal, dead airspace inside, insulation, and material that gives off steam when heated.
For protection against forced entry, UL has a rating in time for entry with tools (TL) torches (TR) and explosives (EX). You will RARELY find a forced entry rated gun safe, because the maker has to provide samples to UL for them to destroy, and pay a healthy fee to have safes rated. I used to do some work involving highly rated safes, such as those used by jewelers or for classified documents. A TRTL60EX15 is rated proof against ANY entry with ANY tool or cutting torch for 60 minutes, against entry with explosives for 15 minutes, and will cost you as much as a nice Mercedes!
There are also very few residential burglars that will have the expertise and very pricy tools for a forced entry. It takes more than a screwdriver and a tire iron.