As I understand it, you may purchase a long gun out of state if both states allow it and you do the transaction at a FFL place of business (which is registered with the BATF). From there website:
"A person may only acquire a firearm within the person’s own State, except that he or she may purchase or otherwise acquire a rifle or shotgun, in person, at a licensee’s premises in any State..."
This is what I believe pertains to someone traveling to another state to buy a long gun.
As to the OP question:
"...curio or relic firearms may be transferred in interstate commerce to licensed collectors or other licensees."
that's correct, but the FFL premises requirement is true of any transaction by a FFL. It' has GOT to be the dumbest rule in the GCA, one I've lobbied to have changed, but as a FFL I can only complete a transaction on my licensed premises or at an exempt event (gun show). Even if I do every bit of the paperwork exactly the same I can't meet you somewhere and conduct the transaction.
With cell phones and the internet everywhere I can do the forms and run the background check from my car. If I do the work properly I have no idea why it matters where I do it.
Long guns are basically governed by state law, which is why I kinda skipped them for C&R. If it's legal in the buyer's state of residence and legal in the state of transaction then it's legal to buy the gun and take immediate possession and transport it back to the state of residence.
The tricky part is that it's the FFL's responsibility to know if it's legal in both states. In my home state that's easy, Kentucky has no special laws on the subject, but knowing the other 49 states is a pain. ATF puts out a CD with info on it, but the laws are changing too quick for that to be 100%.
that's where the C&R complexity comes in, b/c different states have different rules for them, and FFLs are afraid of running afoul of the law in some other state they don't know by selling a gun illegal in that state to a C&R who takes it home. They figure a 01 FFL is more likely to be compliant and/or somehow protects them more if they sell to them versus a C&R or a regular buyer. Not saying that's right, but it's the fear of doing something wrong that makes them so conservative.
Federally interstate in person long gun sales are fine, even for non C&Rs, and with the C&R you can do the same with C&R handguns, but then the state laws come into play and that's where it gets confusing.
There is also some debate about a gun being on the C&R, but that's usually simple enough to resolve. Though mkk41's post shows just how little people know about the C&R rules. Like I said I've read a lot on all the regs and by no means think I'm 100% on them, C&R or otherwise. Too many rules and regs and unclear paragraphs and contradictions IMO.
