Curious as to what was considered "antique" in Canada, I asked almighty google, which returned this from the RCMP. An 1866 doesn't qualify since it's a repeater. Basically it includes muzzle loaders and larger bore single shots made before 1898.
In the US, the ATF defines an "antique" a bit looser, and an 1866 appears to qualify since the ammunition for it is no longer manufactured.
Here is complete definition of Antique in Canada
Types of antique firearms
The following firearms are antique firearms under the Regulations Prescribing Antique Firearms.
Black powder reproductions
Reproductions of flintlock, wheel-lock or matchlock firearms, other than handguns, manufactured after 1897.
Note
All other reproductions of long guns are considered non-restricted firearms. They don't need to be registered but a licence to possess them is required. As an example, reproductions of percussion cap muzzle-loading firearms like American Civil War Enfield and Springfield rifles are considered non-restricted firearms and not antiques.
Rifles
Rifles manufactured before 1898 with the following characteristics:
able to discharge only rim-fire cartridges, other than:
.22 Calibre Short
.22 Calibre Long
.22 Calibre Long Rifle cartridges
able to discharge centre-fire cartridges (whether with a smooth or rifled bore), have a bore diameter of 8.3 mm or greater, measured from land to land in the case of a rifled bore, with the exception of a repeating firearm fed by any type of cartridge magazine
Shotguns
Shotguns manufactured before 1898 with the following characteristics:
able to discharge only rim-fire cartridges, other than:
.22 Calibre Short
.22 Calibre Long
.22 Calibre Long Rifle cartridges
able to discharge centre-fire cartridges, other than 10, 12, 16, 20, 28, or 410 gauge cartridges
Handguns
Handguns manufactured before 1898 with the following characteristics:
able to discharge only rim-fire cartridges, other than:
.22 Calibre Short
.22 Calibre Long
.22 Calibre
Long Rifle cartridges able to discharge centre-fire cartridges, other than a handgun designed or adapted to discharge:
.32 Short Colt
.32 Long Colt
.32 Smith and Wesson
.32 Smith and Wesson Long
.32-20 Winchester
.38 Smith and Wesson
.38 Short Colt
.38 Long Colt
.38-40 Winchester
.44-40 Winchester
.45 Colt cartridges
Safety regulations
Please see the section on Firearms safety.
Black powder firearms
If you possess or are planning to acquire a black powder firearm, whether a muzzleloader or a firearm that discharges black powder cartridges, you should be aware of requirements that may apply to them under the Firearms Act. There are no licence and registration requirements for antique firearms.
Muzzleloaders made before 1898
All black powder muzzleloaders made before 1898 are considered antique firearms. Antique firearms are exempt from the licence and registration requirements set out in the Firearms Act.
Muzzleloaders made after 1898
All matchlock, flintlock and wheel lock long guns are considered antiques no matter when they were made. Like older firearms of these types, they are exempt from the licence and registration requirements set out in the Firearms Act.
Percussion cap long guns and muzzle-loading black powder handguns made after 1898 are not considered antiques even if they are copies of an earlier antique model. Newer percussion cap long guns are classified as non-restricted firearms. Newer handguns, including matchlock, wheel lock and flintlock handguns made after 1898 are classified as restricted if their barrel length is over 105 mm (about 4 inches), or prohibited if their barrel length is 105 mm or less.
There are a lot of reproduction firearms on the market. In addition, some firearms were made over a period of several years spanning the 1898 cut-off date. If you possess or are planning to acquire a percussion cap firearm or a muzzle-loading handgun, you need to know if it was made before or after 1898 in order to know what rules apply.
Firearms that discharge black powder cartridges
A firearm that discharges black powder cartridges might be considered an antique if it was made before 1898, but not necessarily. It would depend on the caliber or gauge. For example, a shotgun that discharges 12 gauge centre-fire cartridges would not be considered an antique no matter how old it is. More information on which ones are antiques is available by calling 1-800-731-4000.