Looks like fun, it’ll be supervised by a trained gunsmith to ensure I don’t make any mods that would get us in trouble.  He’s doing the welds.  Any feedback?  Mods please move this if it’s in the wrong forum.

Nope, but I'd like too. Would go well next to my Garand and 1911.

BTW, "Anyone ever built a STEN bun from a kit?"

I looked into it real hard last year. I want to but I was playing on the Indianapolis Ordnance semi auto kit. I found the price to be 700$area for me with a 16" barrel. However I don't have an apparatus to weld so that would add a lot to the build price. With that being said, if I were to own another 9mm carbine it would be a Sten or Lancaster or a Russian ww2 smg. 8 had an AR9 and felt like it was a lot of money for meh. It felt like my 22lr build with a little bit more kick but still just an AR.

Built one twenty years ago from a registered tube and a parts kit.  Nothing to it if you know how to weld.  I don't, and took it to a crusty neighborhood welder who put it together for me in a matter of minutes.  Worked fine - the tolerances are very forgiving in this firearm.

I've built 1. Or 6. After the first one they are super easy. I built all mine off of Indy kits except I made the tubes myself. Nothing to it, the tolerances aren't critical. All mine have run right out of the box. You could probably silver-solder and rivet a MKIII together without having a welder if that is your hold-up. The semi-auto kits are a little pricey but they are excellent quality. I'd rather pay more money than have to tinker around with one to get it to work.

Easy with Indy kit and semi-auto bolt.  Just do a lot of reading to make damn sure you don't build a machine gun, or something that the ATF thinks is too easily converted to a machine gun.

My first ran perfectly at the range.  When I got back home to clean it, I noticed that the extractor was still sitting on my bench.  The simple blowback action had no trouble ejecting el cheapo Russian steel cased 9mm without an extractor.