I'm hesitant about USPS - I've had to file claims for lost packages (a pain) and the latest gaff was a handgun left on my porch.
Of course, that would be the shippers fault if they didn't ask for adult signature.
Did you take the gun to a LGS to have them transfer it to you?
No, I have an FFL - It was suppose to go directly to me. But, it should require an adult to sign and not just be left out on the porch for the afternoon.