I need to send a mg receiver to a class 3 dealer out of state for repairs. Which shipper do I use. I have seen that USPS says they will not ship "concealable guns" this is a part so does that still apply? I have read that ATF recommends a filing a form 5, but not necessary. Does it have to be shipped from a FFL and back to them. What is the safest & legal way. I don't want it "lost in transit" Thanks.