Fairly simple......
Look as to what others have made and are selling as 80% receivers........make up the item to be submitted to BATF.....then ship it to the NFA Tech. Branch for determination.
Basically now, it seems more like someone has made more 100% receivers than they can sell (posibly someone trying to push a "Groooop" Deal here-?)........but either way, he will be able to sell more with the 80% receivers (at a lower price) and a submission to BATF NFA Tech. Branch will take a little time which doesn't start until the submission is received at BATF.
Proper/straight "TIG" welding seems to be a challange for a lot of Board-Members.
If "Brian" submits a welded receiver without trigger-group/ejection-port-slot, etc. machined/punched-out......it should pass BATF NFA Tech. Branch as an 80% or less receiver.............just the four-quarters that he stamps out, TIG welded together as an entire unit (with the front barrel-support welded in.....and the ratchet-plate correctly welded on) and then welds ground-down to insure no pockets in the welding......all very simple. It doesn't have to have the Trunion/"Cam-Piece"-holes-cut-out .
He might even be able to install the Barrel-stop/rear-weapon-mounting-block/rear-sight-bracket.........I don't believe that these would take it past the less-than-80%-point.
It mostly concerns the rear part of the receiver.......no holes for the trigger-group.......no holes for the ejection-slot.........no work done on the charging-handle-slot......and no engraving at the left-rear of the 80% receiver.
Look at the current AK-47(AKM) series 80% receivers being sold.......with rails and ejectors welded in..........dimples on sides and mag-well.......just magwell not completely machined and no holes drilled for FCG.
Like anything........he will have to ask and make a submission to BATF for determination .
Regards, RichardS in MI.
US Army, Retired.
Blanksguy2001@chartermi.net