Thanks for the videos! The shotgun assembly makes more sense. I'm working mostly with the original files, and have noticed some changes. I think they may have solved some of the issues I've seen.
Having built some long blaster rifles - BlasTech A290's and A300's from Return of The Jedi and Rouge One - both resin and FDM, my concern has been keeping them from snapping in half when being handled and carried around while in costume.
I've made some modifications to use a 1/2" aluminum tube as the "core":
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I created some simple bushings in Tinkercad. One to center the "barrel" in the end of the receiver:
View attachment 1351125
and the other on the "pilot buff"
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This gives the receiver, shrouds, Thompson ex block, and barrel shroud something to hold on to
I had to remix the bolt and "cut" a 15mm hole lengthwise
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I had to sacrifice most of the internal functionality of the Thompson, but the bolt still slides back and forth manually. I intend to put electronics for sound and ammo counter, so as long as it makes noise and the counter decreases I don't think anyone will really mind. The ex block and "hex tabs" are slightly out of alignment
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You can see the ex block is at a slight angle - the rear is about 1mm lower than the front. This pushes the SPAS cage down away from the receiver, and the exterior shrouds up. I'll try softening the hex tabs (hot water or a controlled heat gun) and see it it can be put in alignment.