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Made some progress with the resurrection today.
After failing to get the housing running true in the second fixture, I took off the three jaw chuck with the fixture attached and put on the four jaw one with the first fixture so I could manipulate the housing until the barrel's OD was running true. Once I achieved that it became apparent that the thin end is oval by about 0.04 - not a major problem I guess, but it shows that the person that made it, didn't not know about internal stress in stock aluminium or didn't give a damn. Then I re-machined the big end, removing the minimum amount material, paying special attention to the inside of the lip that one of the lenses sits against. That lip had a shocking runout - I had to remove about half a millimetre from the inside face to get a nice continuous surface.
After this I swapped the chucks again hoping that this time the damn thing will run true in the second fixture, because the end has been trued up and the thread seemed concentric with the barrel. It did not. And that meant one thing: The butcher that cut the big thread at the end, did clock up that end but id did not worry about the fact that the other end was running out. So the thread was cut on a slight angle. I had to swap the chucks again. Went back to the four jaw one with the first fixture and re-cut the big thread. It was already a bit undersize so now it is even more so but it is straight. A loose thread should not cause a problem in this case. While I had the thing set up in this manner, I used a boring bar to open up the inside diameter until the eccentricity was gone. My boring bar was only long enough to go in about half the length of the housing. Once I swapped the chucks again and found that the housing was finally running true in the second fixture, I was able to complete the boring of the ID from the thin end, and also recut the short M82x1 thread. At this stage I also had to cut a new internal thread, which had to be a non standard M72.5x1 because I did not want to make the barrel any thinner.
Absolutely amazing that there were no two features on this part that were consistent with each other.
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