No experience with Registered Mail, but I recently used FedEx Priority Overnight to ship my Oly/PAWS RR from an out-of-state dealer to my local FFL/SOT.
I used my FedEx account to generate an e-mailed prepaid shipping label for the out-of-state dealer.
The MG got to my FFL/SOT safely the next day. The only glitches were:
1) The status updates during transit were not timely, no messages from after package pickup until arrival at my local FedEx station, so I was worried it had disappeared en route; and
2) Priority Overnight delivers before 10:30 a.m., my dealer wasn't open yet when the FedEx guy came at 8:30 a.m. and had to re-deliver at noon
I'll probably use Standard Overnight next time (deliver before 3 p.m.)
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I've also used FedEx 2Day to ship guns to and from John Andrewski for upgrades and refinishing, no problems at all, even the status messages were on time, go figure.
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I never get insurance from FedEx, as the rates are so high that you might as well get a firearms insurance policy for all your stuff from a reputable insurer - I use
Eastern Insurance (my only connection is as a customer), which was recommended in this thread:
Anyone have firearms insurance for NFA stuff? - AR15.com