This is called a Serpentine (supposedly due to its resemblance to a snake although I can't see it myself):
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I've drilled out the barrel but there's still a bit of fettling needed to clean up the joins - it's only dry fit together at the moment.
View attachment 100980
View attachment 100981
I've drilled out the barrel but there's still a bit of fettling needed to clean up the joins - it's only dry fit together at the moment.