I can see the RCMP letting something like manufacturing pseudo-realistic receivers slide, I cannot see them letting the manufacturing of realistic receivers slide. It's illegal to manufacturer replica firearms in Canada. People who build entire guns out of aftermarket guns technically break that law, but so few people do that and on such a small scale that it's not really an issue. If you start mass production of realistic receivers, that's going to change.
"The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."