Is a Winchester model 1873 made up through 1898 & chambered for the .44-40 an Antique by the BATF definition or not. My understanding is that it is so classified even though it fires a center fire cartridge which is still readily available. If it were made in 1899 or later it would not be considered an antique nor would any replica of it. On the other hand a replica of the .44 rimfire Henry would be because .44 Henry rimfire ammunition is not readily available.
This is one of the real gray areas in the mishmash of regulations regarding the status of certain guns. I've seen them handled multiple ways but to my knowledge no one has ever been charged with a violation for selling a pre 1899 gun as an antique regardless of what cartridge it was chambered for.
Jim
