Depends on your definition of "antique" The official definition is:
(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
(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.
Is this what you have in mind?
Dean