I figured a rebarrel was going to be long gun but I suppose its possible it could have referred to a revolver or something as well.
Anyways, here is a summary of my experiences with the different carriers:
USPS - If you have someone who knows what they are doing, this is the cheapest way to ship by far and their expedited services are nice and fast. Most times you will go there and their immediate answer is "we can't ship that". Look up the rules on their website and you will see that an individual can ship a LONG GUN ONLY to a receiving FFL. They will NOT ship a handgun for a private individual without a FFL.
UPS - Very easy to work with. Bring a copy of the FFL that this is going to and present it to them with your ID. All you need to write in the description is "LONG GUN GOING TO FFL, NO AMMO INSIDE" (pistols have to be overnighted and is quite expensive). They might revise it a bit to say something like "adult signature required upon arrival". Probably the most costly option but I think they have the nicest tracking. Most gunsmiths I have dealt with use Fedex or USPS because of ease of return shipping. Never had an issue with them losing a package, closest call was sending a package from me (in MIchigan) to Seattle, WA when it was supposed to be going to California...oops. Only downside is don't expect them to pay out on their insurance, you are almost better off not paying the extra. With all that said, I use them most because of their location relative to my work. You HAVE to ship from one of their customer centers or whatever they call them, not a drop location or store.
Fedex - From what I have seen with them (or at least the ones around me), they are the carrier with the least questions asked. They used to not even ask me for a copy of the FFL, just a verbal recognition that it is going to a FFL. Middle of the road prices and decently fast services.
Anyone of them can do it for you, Fedex or UPS usually have more competent people behind the desk than USPS.
