Good list of procedures for registering a gun in DC
Right here. A bit more complicated than in AZ, where the checklist consists of "buy a gun."
I had a person tell me, years ago, that when they moved here they called the Sheriff's Office to find out how to register their pistol. The answer was "you can't." She said that she just didn't feel comfortable with an unregistered gun, could she send them a letter with the data. The deputy responded that she could, but they' probably toss the letter, since they have no files for anything like that.