An active duty military member may establish residency by presenting permanent change of station (PCS) orders and a valid military photo identification card (see ATF Ruling 2001-5). The PCS orders may be either paper or electronic, as stated in the Form 4473 instructions for item 26c, “Licensees may accept electronic PCS orders to establish residency.” 

Spouses and other dependents of an active duty military member may not claim residency using PCS orders, as 18 U.S.C. 921(b) applies only to members of the Armed Forces.

A military member claiming residency in a state in which he or she is present with the intention of making a home must demonstrate that residency to the federal firearms licensee (FFL) by presenting a valid identification document, or a combination of valid, government issued documents, to satisfy the identification document requirement.

[18 U.S.C. 922(t)(1)(C), 27 CFR 478.102(a)(3), 27 478.124(c)(3)(i)]