+1.
I used to get some grief when mailing firearms (and I mail a lot of them). It took nothing more than making an effort to get to know the employees there, and letting them get to know me. Now they are fantastic to work with.
I can tell you that if you immediately tell the employee that they are wrong about the regulations, they will most likely dig their heels in and "prove" that YOU are wrong, no matter what the truth may be.
A little tact and respect can go a long way when dealing with government employees.
