Nevyan

Hello all, I have searched but am unable to find an answer to this question. When I sell my shotgun, privately, to someone with godkjent søknad and legitimasjon of course, and after sending in the white copy and the relevant våpenkort. What is the procedure for purchasing another shotgun? Same caliber and type, basically selling my Baikal o/u and buying another 12gauge o/u. Many thanks for your help. Neil