Insurance is going to depend on types of firearms you are checking. Here is some info on insurance options:
http://www.smartertravel.com/travel-advice/extra-baggage-insurance-why-you-may-need-it.html?id=5527781
I cover it through my homeowner/personal property insurance and NRA insurance. Just check with your agent(s) beforehand so you know where you stand with all of it and know what your options are.
From my personal experience, airlines are a PITA to deal with on lost luggage. I have never lost a firearm in checked luggage, but I know it happens. They will only give you depreciated value on any of your luggage contents, so if you are traveling with a 50 year old firearm, their depreciation tables are going to severely discount the value (even though we know that firearms appreciate, not depreciate - right?). And if it is a collector type piece, they probably won't cover the "collector" value - check their disclaimers. If your homeowner/personal property insurance is replacement value is where you need to be, and ensure they will cover what the airline won't cover.
Good luck with it all and safe travels!