Thanks Keith. I still find the Code confusing:

(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;

It seems they are intending to include everything but centerfire breech loading guns.

(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...

I wish they just left 16A as "any firearm manufactured in or before 1898.