yes I made one for my deactivated tommy. I didn't bother to screw cut into the barrel because it will never fire anything. I did something like the diagram below. turned it out of bar stock and drilled out the 10mm barrel opening.
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barrel3.png [ 2.9 KiB | Viewed 3392 times ]
It is attached with a solid insert into the original barrel, exactly the same diameter of the barrel and hammered in so that the rifling grabs it. solid as a rock.
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barrel2.png [ 716.02 KiB | Viewed 3392 times ]
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barrel1.png [ 244.37 KiB | Viewed 3392 times ]
anyway I've just got to get through a mind numbing day at work and then i'll get some measurements over.