Dual residency...
I wonder if I could use my in-laws place. My wife is still a resident at that address.
Whoa!, your wife is still a resident there? Hell man, let her buy the AR15 or handgun in VA and then bring it back to DC for registration (or buy the AR lower and keep it in VA untill you want to assemble the rifle and bring it to DC for registration). YOu must remember though that she must be residing in that state when she makes the purchase, she can't just drive there and then drive back with the gun that same day.
State of residence. The State in which
an individual resides. An individual resides
in a State if he or she is present in a State
with the intention of making a home in that
State. If an individual is on active duty as a
member of the Armed Forces, the individual's
State of residence is the State in
which his or her permanent duty station is
located. An alien who is legally in the
United States shall be considered to be a
resident of a State only if the alien is residing
in the State and has resided in the
State for a period of at least 90 days prior
to the date of sale or delivery of a firearm.
The following are examples that illustrate
this definition:
Example 1. A maintains a home in
State X. A travels to State Y on a hunting,
fishing, business, or other type of trip. A
does not become a resident of State Y by
reason of such trip.
Example 2. A is a U.S. citizen and
maintains a home in State X and a home
in State Y. A resides in State X except for
weekends or the summer months of the
year and in State Y for the weekends or
the summer months of the year. During
the time that A actually resides in State X,
A is a resident of State X, and during the
time that A actually resides in State Y, A is
a resident of State Y.
One caveat though, only your wife could possess the handgun or rifle registered to her (when in the home and used for self defense is a gray area though) when in DC (when outside of DC it is generally ok for you to borrow her firearm for sporting use no problem).
You using her place as a residence instead of her may be a problem and a bit sketchy. You have to have the intent to make that location your other residence and to reside there. The FFL is going to ask you or your wife for proof you reside in VA and that can be a VA driver's license or other identification with utility bills with her name on it of a residence in VA.