There is a sticky in the General Firearms forum and if you call the CFO for your short term ATT, they will tell you this. You do know you need a short term ATT for the post office, don't you?
"I was just looking at Canada Posts regulations on mailing firearms and this is what it says;
4.3 Firearms (including imitation and replica firearms)
Please contact the Canadian Firearms Centre at
www.cfc-cafc.gc.ca or by calling 1-800-731-4000 to determine whether it is permissible to ship your firearms.
When it is determined permissible to ship firearms, they must be shipped as follows:
Customer Type --------- Service To Be Used
Non-contract Customer -- Regular Parcel with Signature
Contract Customer ------- Expedited Parcel with the Proof of Age (18 or 19) with Signature option using Electronic Shipping Tools (EST)
Firearms cannot be shipped via air. The Customer is solely responsible for meeting all Canadian Firearms Centre regulations.
NOTE :
Visit section 6.3.1 “Mail Addressed to Children” of the “ABCs of Mailing” chapter for an age of majority by province or territory listing.
There cannot be any ammunition in the firearm or in the package. Bullets, cartridges and other ammunition are dangerous goods and cannot be mailed. These items fall under Class 1 (Explosives) of the CanadianTransportation of Dangerous Goods Act.
Customers who wish to ship firearms must :
unload the firearms
attach a secure locking device to the firearms
lock the firearms in a sturdy, non-transparent container and
remove the bolt or bolt carrier from any automatic firearms (if removable).
Firearms cannot be shipped via air and cannot have any markings on the outside of the packaging. The Customer is solely responsible for meeting all Canadian Firearms Centre regulations.
NOTE :
For more packaging tips, refer tosection 4.2 “Package the Item” of the “ABCs of Mailing” chapter.
...I guess the "priority" post requirement has been dropped. Nice to know, i.e. in regards to $$$ for shipping."