This lot is in a local auction. Not a common or garden Rolex, auction estimate 70 - 90 K sterling.
https://www.byrnesauctioneers.co.uk/catalogue/lot/b3a72ab528de2950d498944cd8c3d3bf/19183007e5777e34776cf9ce10500cfa/the-spring-two-day-fine-sale-lot-400/
David.
This may be in the wrong section and if so could a moderator move it please.
The Wilson 55 auction site has a couple of of the above, one an unfired example and the other a late model Jungle carbine.
Try wilson55.com if you are intereste.
David.
I might be tempted to find a bolt in the same thread as the mor and screw it in tightly and pressurise it with a bit of compressed air and see if you can trace a leak.
David.
I am sure the Delrin washer isn't there to catch hot gas. The mod shouldn't be leaking gas backwards. I think as previously stated it needs checking and possible replacing.
David.
I certainly found it well worth doing. Not just the course which was very informative but there were people there who had lots of experience in different areas so the Q & A sessions and the coffee and lunch breaks were very informative too.
David.