I've used AmmoSeek a few times when I was hunting down some 9mm and .223 ammo. Overall, I found it pretty useful since it searches a bunch of retailers and helps me compare prices without having to jump from site to site. Most of the listings were accurate, but I definitely recommend checking the retailer's site for availability before making any assumptions; sometimes the stock levels aren't updated in real-time. I did come across a couple of sketchy sellers, so always check reviews if you're unsure. Stick to the sites that seem reputable and have decent customer feedback. It's a handy tool for finding ammo, just use a bit of caution and it should serve you well.