Many thanks all. No burrs, factory rounds plunk in quite satisfyingly and drop out on their own weight. Using a jeweler's loop to look at the extractor cut with a shell in the chamber I could tell that there was almost no rim to grab compared to the original barrel. I VERY carefully used a small file to make the cut deeper and now it is ejecting some fired hulls without problem.
Good to hear you found the issue. I have only had that problem once before - maybe a dozen years ago and you're correct in filing slightly to allow the extractor to engage.. Nice job.
Now for the second question. It appears that the barrel hood is a separate piece which has been screwed onto the barrel. Is this possible? Is it safe?
Yes - as the others stated above..
