[phyrrus9]

Update: I was in discussion with a youtuber that often manufactures guns about methods for testing this gun, and got a good set of responses as far as what type of properties the metal might need to have, ideas for setting up slam-fire testing rigs, etc. I'm pretty sure this prompted him to go 1 level less safe and make a 12 guage (non-NFA length) barrel out of electrical conduit. The results surprised me.

https://www.youtube.com/watch?v=O-_D0lglocI