Got to shoot a full auto UZI a few years back and was surprised on how controllable it was. Not going to spend $20K to get my own FA UZI, but Christmas before last the Fat Man brought me a $175 Model A UZI parts kit, $75 repair section (922R), $40 USA grip and handguard set (922r times 2), $20 charging handle 922R. Green Mountain was out of cheap barrel blanks (922r), so the kit sat for over a year until GMB sent me an email last month that the blank I wanted was back in stock. So the parts were dusted off and the build was restarted. Still not done with it, but it's done enought that it's been test fired which went off without a hitch. Once it's marked I'll submit a form 1 SBR (I hate the long barrel) and down the road when the tax stamp comes the barrel will be shortened to 10.5".
Probably take me a couple weeks before this gets parkerized and the form1 gets sent off for, so bear with me.
The Uzi build is similar to an AK build where there is a correct receiver length, but mainly you want the top cover to fit and can adjust the length a little either way to acheive this. Slightly too short and the top cover will bind but it can be trimmed. Slightly too long and the top cop will fit sloppy but can be built up with weld. The UZI drawings show 13.510" for the sheetmetal receiver minus the back plate and front trunnion. That's within .010" or so of where this one ended up after welding. The top cover fits well. The repair sections are slightly shorter than the original receiver, so make sure the bottom and sides are aligned for welding and don't worry about the heigth of the sides. The repair section for this build came with the denial bar already welded in. I made a welding mandrel to hold the back plate, repair section, front stub and semi auto feed ramp in position for welding. The 1/2" stock bolt hole is in line with the barrel bore, so I just turned a piece of aluminum to fit the trunnion, feed ramp ring and threaded it for a 1/2" bolt. Worked like a charm. The ring on the feed ramp needs to be aligned with the barrel and also be tight to the bottom of the receiver. The jig held it there for welding. Pic two the feed ramp hasn't been welded on yet, but the grip mount and handguard mount have.