Please don't let this descend into an argument about the laws and regulations regarding legally building/owning AOW/SBS firearms. I know all about them, and that is not what I'm asking.
Having said that, I have a few extra barrels and mag tubes laying around. I have always wanted to buy a Serbu Super Shorty, and I've been thinking about just trying to find a bare receiver and building one myself. If I were to find a receiver I could legally use to do this, how would I go about cutting the mag and barrel down to probably around 8"? I've cut many barrels down to 18.5", I usually wrap it in masking tape about 1/16" longer than I need, hacksaw it off evenly, and file it to a uniform edge and paint it. Always works great, but given the length, I've never had to cut the mag down.
To go as short as I want it, I'll have to take the lug off the bottom of the barrel, and cut the mag tube back and somehow cap and thread the end and reattach the lug further back on the barrel. Has anyone tried anything like this?
I'm asking here rather than the NFA forum because the same procedure could theoretically be used to extend a mag tube to conform to a longer barrel, so I think this is relevant to more than just NFA applications.
On a side note, if anyone has any idea how or where to buy un-assembled receivers for Mossberg 500's, please post it here.