Gun Broker has a tutorial on legal shipping practices, and a downloadable PDF of the USPS regs and other carriers, on the right hand side of the Home Page. Read and understand them. I also carry a spare hard copy to leave behind with both UPS & USPS staff who "think" they know the ATF Reg's ...and don't. Very Helpful.
Remember Aesops Fables outcome of the "Scorpion & and the Frog's" crossing the river when they get to other side
a LOT of Money doan't buy you ANY Class..old South Oak Cliff mantra
Those who fail to learn from History are doomed to repeat it...Santayana