Kutter,
I think "nibbing" is limited in the length to which cases can be extended, I believe it saw use in making 45-90 from 45-70 before Starline started making it. I also questioned whether hornet cases could be "redrawn" to the required length, because of the same concerns you had. I haven't tried "retubing" because a friend (more experienced than I) tried to make 9.3x72R norm. that way, unsuccessfully. The use of .223 (or 222 also not too common) would require procedures/equipment that mostly only those engaged in the business would have but would be possible. I have, in my "pile" a couple 8x72R cases that were made from 30-06 and would have required similar procedures. Since post WW2 producers are mostly gone, I would be happy to find someone that can do this work commercially now. I am not convinced that lathe turned cases have the correct grain structure but can see the possibility for black powder cartridges that are large enough to permit thick " everlasting" type case walls.
Mike
