Also, be very careful trying to bring gun parts, ammunition etc from the States.
To import a barrel you need a U.S. export permit
"Canadians Importing Firearms, Parts, Ammunition, Powder, & Primers From the U.S.
A Canadian on a visit of less then 90 days cannot take possession of a firearm, either purchased from a dealer or as result of private sale. Under no circumstances may you take possession of the firearm when in the states.
All such sales (dealer or private) must go through an FFL. The FFL must ship the firearm to Canada or arrange to have it transported to the border.
http://www.atf.gov/publications/download/p/atf-p-5300-18.pdf
In addition to FFL cost, the buyer will have fees for shipping and duties. Duties will vary depending on country of manufacture.
Items which usually need an export license are frames, receivers, barrels, triggers, sears, ejectors, magazine tubes, scopes (...)"
Barrels cannot be shipped outside of the U.S.A.
There are strictly enforced rules that go along with gun parts.
A Gun Part is “any item necessary to the operation of a weapon”. Many parts fall within this category, such as triggers, magazines, grips and barrels.
Current Regulations require An Export License for all Gun Parts exceeding $100 (U.S.)