Just a few thoughts about ammunition sales, since without ammunition a firearm is just an expensive baseball bat.
A couple of years ago I built one of the AR15 clones - for several reasons including because I could and I wanted to see how it worked. I purchased almost all the parts online, legally, and bought the receiver from a licensed dealer - where I had a background check. All above board and legal. (the receiver is the critical part that is needed to make it a functional firearm - the other parts on their own are just hunks of metal and plastic)
When I wanted to take it to the range I needed ammunition. Since centerfire ammunition is not exactly inexpensive, I thought I'd try one of the online sites. It was very easy to order quite a large amount of ammunition online, and more surprisingly other than a trivial check (I asserted that I was over 21 and not a felon) there was little more than a check of my credit card.
Something is wrong with this.