I drilled and tapped the stub before I inserted the new barrel for a scope rail. I used a mig welder to tack the barrel to the exit end of the stub where the forearm hides it. I had the barrel in the freezer first and only put on a small weld so that I wouldn't damage the barrel inside. I also put a few small welds on the face of the barrels on the chamber end and ground them down flush. I took it out and fired a couple of test shots, blued it, mounted the scope and shot about 20 shots total to get the scope zeroed and to test it. I had to thin the ejector a little and notch the barrel for it.
I have to make sure the shell catches on the lip of the ejector when loading since it isn't rimmed (close the barrel partially) or the shell falls all the way in under the ejector.