Sprinklers aren't like the movies. There is a link that melts at a specific temperature which opens that sprinkler head only. Residential systems are costly and main not help your insurance. I thought researched the idea years ago, and insurance companies prefer the low risk of a fire to the higher risk of leaks.
According to my fire marshal friend, the water used by the FD turns to steams and permeates pretty much everything. So your guns may be rusting away even if the safe didn't get touched by fire. This happened to my dad's machinist tools when the business he worked for burned. His work area was small and was barely affected by fire, but his stuff was trashed by the time he could get to it. Like him, you may not have access for some time, as the FD determines when you can re-enter your house.