Well, as I promised the couple guys who were wanting updates on this project, here goes.
I contacted the tech last week to see what the story was on the issuance of this certificate, and whether it was a mistake. I asked him if the position of the RCMP lab had changed as to what part was registered on a sten. He said he would get back to me. I heard nothing back for about a week, so I contacted my local firearms officer, who looked up the registration certificate. The classification of the firearm had changed from "restricted" to "under review". I emailed the CFC tech again and asked him what was going on. He phoned me the next morning and told me that the cert was a bit of an error, and that their position that the magwell was the registered part had not changed. Since I had recycled (good for the environment you know

) an origional mk2 British housing the gun was likely going to be considered a converted auto/prohib. He said it would require a new magwell. I asked him if I would be making a prohibited item, as it would be a machine gun part, but he said not to worry, as it was for a restricted gun.
That was yesterday morning.
I headed out to the shop to see what I had for scraps of metal the required thickness to take on such a project. The origional magwells are approx .100 thick, so I decided to go with 1/8" plate. The early sten magwells were comprised of two parts, a short piece of round tube, and a rectangular piece welded to the side of that. The tube has a inside diameter of approx 1-1/2 inches, and by what I have always heard, it is not a common size. Also, if I had to order in the tubing from Brandon, I would get stuck ordering in 24 feet of it, and likely have to wait weeks.
So I went to Brandon and bought some 10' long pieces of steel plate 4" wide and 3" wide.
In the first series of photos below you can see the building of the tube part. I turned an old Bren gun carrier roadwheel pin down to the proper diameter and bent the steel plate around it. I welded up the seam and cleaned it up a bit on the lathe. The surface was a bit rough, between the rust that had formed from it's outdoor storeage, to the hammer marks from my crude work.
That was it for yesterday.
Today I made up a mandrel and bent the 1/8 plate for the rectanglular tube portion. In the photos below you can see the progress.
Now came the time to join the two parts together. I tacked it together, then attached it to the SAS-3 receiver to cycle some dummy rounds. It didn't really like the position it was in, so I cut the welds and moved it back about 1/16 an inch. It now cycled perfectly.
With the welds completed, I just had to clean up the work a bit. Not too clean mind you, it is a sten after all. Then, to finish it off I stamped in the identification onto the housing.
Now I have submited the photos to the CFC, and await further word. There is a good side and a bad side to all this. Good side is that it can be done. Bad side is that if you don't have access to a lathe and welder, and about 10 hours of time to kill, it will be very difficult to make your own housing.
Another good point is that once mine is accepted, sten parts won't be "exclusively for a prohibited gun" which should help make importing parts easier.
More info to follow as it becomes available.