18 USC 921 (a)(16). (A) any firearm (including any firearm with a matchlock, flintlock, percussion cap, or similar type of ignition system) manufactured in or before 1898; and (B) any replica of any firearm described in subparagraph (A) if such replica -- (i) is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition, or (ii) uses rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade.
I have always understood the language to mean that any replica of a pre 1898 firearm would be considered modern if it took a modern cartridge. I think if you read this carefully you will get the same impression.The subsection (ii) is referring to guns mentioned in B.
