The DA's ALWAYS will tell that 'cause they can't READ their wn Rules...what you were told IS True...for a handgun.
Go look at the tutorial and complete explanation on GunBroker, on the right hand side of the home page, and YES...Print Out the USPS regs to take with you.
+ 1 on no external package markings, and address the pkg to the FFL owner or designated clerk using only his NAME and not the name of the store, along with the correct local address and your own address yadda yadda.
Remember Aesops Fables of the "Scorpion & and the Frog's" crossing the river...
... we must hang together, or we will ALL hang seperately, Ben Franklin..
Those who fail to learn from History are doomed to repeat it,Santayana