I found this on the ATF webiste, full text here http://www.atf.gov/regulations-rulings/rulings/atf-rulings/atf-ruling-2010-6.pdf
"A person’s “State of residence” is defined by regulation in 27 CFR 478.11 as “the State in which an individual resides. An individual resides in a State if he or she is present in a
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State with the intention of making a home in that State.” Ownership of a home or land within a given State is not sufficient, by itself, to establish a State of residence. However, ownership of a home or land within a particular State is not required to establish presence and intent to make a home in that State. Furthermore, temporary travel, such as short-term stays, vacations, or other transient acts in a State are not sufficient to establish a State of residence because the individual demonstrates no intention of making a home in that State.
To ensure compliance with this residency requirement, section 922(t) of the GCA requires licensees to examine a valid “identification document” (as defined in 18 U.S.C. 1028(d) and 27 CFR 478.11) of a firearm transferee. This document must contain the residence address of the transferee so that the licensee may verify the identity of the transferee and discern whether the transferee has the intention of making a home in a particular State. Licensees transferring a firearm to a person not licensed under the GCA are required, pursuant to 27 CFR 478.124, to record the firearm transaction on an ATF Form 4473, which requires, among other things, the transferee’s residence address, including the transferee’s State of residence as it appears on the valid identification document.
The term “identification document” is defined by 18 U.S.C. 1028(d)(3) as “a document made or issued by or under the authority of the United States Government, a State, political subdivision of a State . . . which, when completed with information concerning a particular individual, is of a type intended or commonly accepted for the purpose of identification of individuals.” The regulations, 27 CFR 478.11, define the term “identification document” as “[a] document containing the name, residence address, date of birth, and photograph of the holder and which was made or issued by or under the authority of the United States Government, a State, political subdivision of a State . . . which, when completed with information concerning a particular individual, is of a type intended or commonly accepted for the purpose of identification of individuals.” Identification documents include, but are not limited to, a driver’s license, voter registration, tax records, or vehicle registration. As explained in ATF Ruling 2001-5 (ATFQB 2001-4, 37), a combination of valid government documents may be used to satisfy the GCA’s State residency requirement.
ATF has previously addressed the eligibility of individuals to acquire firearms who maintain residences in more than one State. Federal regulations at 27 CFR 478.11 (definition of State of Residence), Example 2, clarify that a U.S. citizen with homes in two States may, during the period of time the person actually resides in a particular State, purchase a firearm in that State. See also ATF Publication 5300.4 (2005), Question and Answer B12, page 179. Similarly, in ATF Ruling 80-21 (ATFB 1980-4, 25), ATF held that, during the time college students actually reside in a college dormitory or at an off-campus location, they are considered residents of the State where the on-campus or off-campus housing is located."
To me it sounds like it comes down to the dealer and if they'd be willing to do the transaction.