[Shmackey]

For shipping overnight to an FFL, can I pack my own cardboard box or do you have to use the nice FedEx boxes?

[Blueduck]

I've used my own boxes twice, pick-up guy did not complain either time. Little shipping slip you fill out even has a box for "other" regarding packaging, so can't see problem.

[Preacherman]

I've almost always used my own boxes, and FedEx has never complained. As long as you remove all old address labels, etc., you should be fine.

A buddy of mine took this to extremes... He wanted to ship five handguns, belonging to him and some friends, for an action job by a nationally-known gunsmith. He wrapped all five securely, and put them one next to the other in a rifle box! Took it to FedEx, shipped it, and insured it for $4,000! The FedEx lady's eyes got rather big, and she commented that "that must be a REALLY expensive rifle in there!" He didn't disillusion her... :D