We've read the law, have you? Antiques are not mentioned, nor are they a part of the definition of rifle/shotgun in the state statute.
Yes, in fact I did read the original draft of Senate Bill 0208 of 2020, which is what I was referring to. The definition of "rifle" in §4-201 of the Criminal Law Article was included by reference in the original language of bill. It defines "rifle" as:
(e) "Rifle" means a weapon that is:
(1) designed or redesigned, made or remade, and intended to be fired from the shoulder; and
(2) designed or redesigned, and made or remade to use the energy of the explosive in a fixed metallic cartridge to fire only a single projectile through a rifled bore for each single pull of the trigger.
(2) designed or redesigned, and made or remade to use the energy of the explosive in a fixed metallic cartridge to fire only a single projectile through a rifled bore for each single pull of the trigger.
That functional definition does not exclude pre-1898 cartridge guns from its scope. There are several sections of MD law that use that definition of rifle (and the similar one for shotgun), but then go on to specifically exempt "Antique Firearms", as also defined in §4-201. SB0208 of 2020, as introduced, did not.