First, talk to you insurance agent.
I found there were two choices, each with pros and cons. First, you can just let your basic home-owners (or renters) policy cover the guns, or you can get a Personal Article Floater.
The personal article floater allowed for a lower deductible, and replacement for almost anything loss, including stuff like "left it at the range", or "dropped it down a sewer pipe". The P.A.F. however, required full disclosure of all articles in advance, with receipts or appraisals. I don't have receipts for everything in my collection, so this was out of the question for me.
Allowing basic home-owners to cover it had the benefit of not requiring full documentation of where the stuff came from and how much it cost. Simple picture record, with serial numbers and descriptions given to the insurance company AFTER THE LOSS is adequate. The drawback for this is that the guns are under a higher deductible than I'd like.
I have USAA, YMMV.
(Will I ever learn it's better to spell check before submitting than to have to come back and do it later?)