This would make things too much easier. Imagine just mailing in a registration like you do when transferring a car.
ii. Bringing the firearm, D.C. Code § 7-
2502.04(c)
The District argues that the “requirement that the firearm
be made available for inspection allows MPD to verify that
the application information is correct and that the firearm has
not been altered or switched with another firearm.” The
District, however, has offered no evidence — let alone
substantial evidence — from which it can be inferred that
verification will promote public safety. The district court
acknowledged as much when it noted that not one of the
District’s four experts “specifically addresse[d] the
requirement that registrants bring the gun to be registered
with them.” Heller III, 45 F. Supp. 3d at 59. The district
court nonetheless deemed it a “common-sense inference” that
“if in-person appearance is necessary to verify the identity of
the registrant, then physically bringing the gun is similarly
necessary to verify the character of the registered weapon.”
Id. Yet common sense suggests a person would not go to the
trouble of obtaining a registration certificate for a weapon
other than a weapon in his possession. On the contrary,
common sense suggests that bringing firearms to the MPD
would more likely be a threat to public safety; as Heller
maintains, there is a “risk that the gun may be stolen en route
or that the [would-be registrant] may be arrested or even shot
by a police officer seeing a ‘man with a gun’ (or a gun case).