I used to order ammo from Sportsmans Guide, as well as a lot of other cool stuff over the years too. The service has always been just fine. If you buy a lot it’s worth it to join their club for discounts. Unfortunately the Peoples Republic of California has banned mail order sales of ammo, not to mention all kinds of other good stuff, like machetes and bison leather jackets (go figure!). I am however still well stocked from what I bought during the Clinton years!
Just checked Google and didn't see that. They require proof of age, but that's it as far as I can tell.