Canadian Oregon anti muzzle load rifle shotgun pistol gun show loophole law fixed ammunition

the US federal definition of “firearm” excludes antique firearms & they include
a 3rd category of non firearm that may not be covered by your state law definition

The federal 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 rim fire or conventional center fire fixed ammunition, or
(ii) uses rim fire or conventional center fire 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, breech block, or any combination thereof.

Oregon law exempts antique firearms from many Oregon laws regulating
the transfer and possession of firearms & defines “antique firearm”
as
(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 paragraph (a) of this subsection if the replica:
(A) Is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition; or
(B) Uses rimfire or conventional centerfire fix..