Actually, most of them will be classed as an ANTIQUE. Under US Federal law, a Curio & Relic is 50 yrs old or older. So, yes, those would be C&R IF ORIGINAL.
The same law defines ANTIQUE firearm as a "loose powder and ball" type gun, OR a gun made prior to 1899. Cupfires, teat fires, lip fires, Crispins, etc, seem to date from the 1860s.
Reproductions are treated a little differently, however. If it is a repro that ammo is not made for, it is still antique. Start making ammo for one, the repro would be a modern firearm. So you COULD have a Plant cupfire, but anyone starts making .42 cupfire ammo, you have a firearm.