Hi Shane, welcome to the boards.
Firearms and firearm parts are typically handled differently for importation purposes.
Because of the Voluntary Restraint Agreement (VRA) signed in 1992 between the US and Russia, *no* Russian/Soviet firearms *not* on the VRA list can be imported into the United States. Doesn’t matter the country of origin, ‘5 years away from a proscribed country status’ or any other of the more arcane rules that may or may not apply. VRA is the supreme rule and makes them unimportable.
Of course, Canada was not involved in the VRA and continued to import Russian SKS45’s through the mid 2010’s before they finally clamped down as well. Having some 25 additional years of imports means they have more (or at least more recently) parted out guns and a more healthy supply of OEM hardware. Coincidentally, We saw this same phenomenon in the US with the influx of Chinese type 56’s from Albania from 2012 to 2019 or so.
Individual Firearms parts except for barrels and receivers are not typically regulated by ATF, but the State Department exercises import/export control of them via something called ITAR. Through ITAR, the government can require individuals and companies to register (at cost of $1500 to $3000 per year) as ‘manufacturers’ if they ‘deal’ in these types of items. Typically, importing a single stock or other component is not considered as ‘dealing’, to get on the radar it takes higher quantities & $’s, but technically the government can drop the hammer any time they see fit. Penalties could be as benign as customs confiscating the shipment to a bad as the government knocking on your door investigating a violation of ITAR, treating you like an arms dealer.
Having said that, most guys that buy from Canada get what they ordered with no issues. I have never heard of anything worse than customs confiscating an individual package. That tiny possibility of something worse happening always exists for firearm users in general though, so it’s certainly something to keep in mind.