When I wanted to make one about 10 years ago I called my cfo and he gave me a # to call for info, it was a gentleman with the rcmp and he told me I could make one , how to get it verified and registered at the time .
He also told me it COULD NEVER BE SOLD but could be inherited once I was gone maybe things have changed since then, you also need a valid pal.
That, in bold, would have been one of those moments where the right thing to do would have been to ask for the reference material that states that.
Before Bill C68 rewrote and superseded a whole LOT of gun laws, there were quite a few laws relating to firearms manufacture and making on the books, as well as some pretty clear requirements for licensing for being a manufacturer, etc.
Most of the laws that said you could not make your own guns, went away when C68 was put in force.
For the most part (like the exclusion of being able to make a prohibited firearm) if you can own it, you can make it. If it requires registration, you must register it. It requires that you register it "When It Becomes a Firearm", which is ill defined, but essentially amounts to "when the RCMP says it has become one", so tread lightly, and get paper on it as soon in the game as you can afford to, lest you suddenly require a lawyer.
Lacking any better source to reference against, there seems to have been a lot of looking South at their system for dealing with self-made guns. As an example, the ATF views an AR forging as becoming a firearm, when the work on the fire control group cut-out begins, not when the Lower is first able to fire a round. So I have read, anyway.
The guys that have done so, say that the RCMP is willing to discuss your plans and will inform you of the "when". If you are doing something outside the previous experiences (theirs), or they may require that you send in the finished product so they can verify that it cannot be easily made full auto (eg: semi auto Sten Gun carbines, etc.)
The difference between making your own, and being a Manufacturer, is poorly defined too, but if you were, say, registering 4 or 5 AR's each month, for any length of time, or you were found to be producing and selling the same style rifle action, again and again, I believe they would be more inclined to think of you as a manufacturer, than as a hobbyist who was making some space for the next, different project.
The full set of Canadian Laws is available online to search through and read. Best if you do so. Just because it is not in the Laws, has not stopped some things from becoming Policy, so be prepared for that too. (eg: the requirement to be a member of a club to get a restricted transfer)
Have fun. Deburr the sharp edges, eh!
Cheers
Trev