That is odd since the link they provide to the RCMP site (once there click the importing and exporting link)
says:
Parts and ammunition
Under Canadian law, you do not need a valid firearms licence to import non-prohibited firearm parts (except for a frame or receiver). However, you may need an export permit from the other country.
You cannot import into Canada
prohibited ammunition
firearm parts that are classified as prohibited devices
This includes handgun barrels that are 105 mm or less in length or parts made exclusively for a fully automatic firearm.
The Explosives Act limits on the amount of ammunition and ammunition components that you can import without an import permit. Generally, the Explosives Act allows you to import up to 5,000 cartridges of non-prohibited ammunition for personal use. However, you may need an import permit for smaller amounts to comply with the laws of the exporting country.
More information is available on the Natural Resources Canada website.