I bought an SKS via AuctionArms.com.
Sent the guy an FFL from a local gun shop.
Gun arrives not at the gun shop, but at my house!
Then, it turns out the gun has the serial numbers ground off!!! Just having a gun like that is a Big Crime.
I take the gun to the shop, cut it into bits, I'm out a bunch of money. I called the BATFE, they say "We're sorry to hear you had a problem" and that's the last I heard of them.
The guy is, of course, long gone. I have no recourse. The money is gone.
Don't buy guns online.