"Well, not exactly. Safes are not burglar proof, only burglar resistant. The most common UL ratings for burglary resistance are TL-15 and TL-30, which means the safe will offer "limited" or "moderate" resistance to opened with common hand tools for 15 or 30 minutes, respectively. There are many safes that do not even achieve these ratings, particularly fire safes. Lower cost "gun safes" often only offer either fire resistance, or tamper resistance.
I'd still bolt it down, for the safety factor if nothing else, and if you have a gun safe of any kind, you are still way ahead of a lot of people. It will deter fast moving burglars looking for easy scores. Someone who really wants your guns will bring the tools and manpower to do it.