First off you cannot send the ammo with the gun, and Canada Post does not allow you to mail ammo at all! Considered an explosive.
Their regs:
3.3 Firearms (including imitation and replica firearms)
Please contact the Canadian Firearms Centre at 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 option
Contract Customer Expedited Parcel with the Proof of Age (18 or 19) option using EST. Visit section 4.3.2 “Mail Addressed to Children” of “Policies” 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 Canadian Transportation of Dangerous Goods Act and Regulations.
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.
http://w w w.canadapost.ca/tools/pg/manual/PGnonmail-e.asp