Hmmmm. I was pretty sure that BRP's semi is a stamped receiver.
Of the home built semis that I have seen, all of them were rewelds. Can you build one yourself? Sure you can. We've amassed enough info and pics to get you started anyway.
I'll see if I can get CWtoyota to chime in and show you guys the pics of his home built semi MG42. It's a thing of beauty.
Oh and the rewelding jig isn't as tough to make as you might think.
Because rewelding is the only economical way to build this, people are very picky about how the demil has been done. IO had the best demils for MG42 kits. Now Angola Armory seems to have the best. I think Dan uses a 6 head CNC torch cutting machine to cut his exactly where he wants them.
Here are a few pics of the different demils out there.
This one is an IO kit. These are very buildable receivers. The demil is very good but it's a 4 cut. Sorry I couldn't find any close ups.
This one is from Angola Armory. These are the best I've ever seen. He missed all of the vital areas with his 3 cut demil yet still legal. This is how they should all be done.
Now for those of you that are sqeamish, you might want to look away. This is a 4 cut demil from a kit bought from Allegheny Arsenal (www.mg34.com site that was linked to earlier). This is the reason we pay more for our kits. You get what you pay for. These are garbage to a builder.
I hope this helps.