As defined in 18 U.S.C. § 921(a)(16) the term “antique firearm” means—
…(A) any firearm (including any firearm with a matchlock, flintlock, percussion
cap, or similar type of ignition system) manufactured in or before 1898; or
(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 [The replica of pre-1898 antique cap and ball revolvers are not designed to use fixed ammunition, but the TC is]
(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; or
(C) any muzzle loading rifle, muzzle loading shotgun, or muzzle loading pistol,
which is designed to use black powder, or a black powder substitute, and which
cannot use fixed ammunition. For purposes of this subparagraph, the term
'antique firearm' shall not include any weapon which incorporates a firearm
frame or receiver, any firearm which is converted into a muzzle loading
weapon, or any muzzle loading weapon, which can be readily converted to fire
fixed ammunition by replacing the barrel, bolt, breechblock, or any
combination thereof. [Once again, the TC is designed to use either and is ALSO readily converted by the replacements of some parts]