I insure all of my guns with state farm. They have a personal articles policy for items like guns, laptops, SLR cameras, basically anything of great value. Its awesome AND cheap. It's $2.00 for every $100 of value. So if you want to insure your glock that cost $500, it'll cost you $10.00 per year. Best part is there isn't a deductible. If your gun is lost or stolen all you have to do is go buy the replacement and bring the insurance the receipt. My agent cuts me a check right in his office, so no waiting weeks for a reimbursement of the funds. Win-Win in my book.
This is what I pay through Shelter. I give my agent an updated list every so often when I need to cover new guns.
The first time I got coverage, my agent came out and took some pictures and I gave him a gun list with values.
Pretty easy process to put your mind at ease.