Clay, do you have dies or have you tried forming one? I’m pretty interested in this but not sure how easy it would be to push the shoulder down that far on a 6BR case. Seems like it could be tricky to anneal far enough down the body and I’d hesitate to try it without but maybe the concern is misplaced.
I owned one way back. On his recommendation, George Kelbly built it for me on a Teddy action when 220 Russian bras had dried up. It was .100” shorter than the parent 7BR case. I had a set of Neil Jones form dies. It took multiple bushings to push the shoulder back. Five or six of them. The cases looked absolutely terrible until they were fire formed. It was a real pain to form them but that rifle had no problems competing with all the PPC’s on the line running surplus H322 or Thunderbird T32 and Walt Bergers hand made 68 FB bullets. That was back when you called and talked to either Walt or Eunice, whichever one wasn’t pulling a handle! Man, I’m getting old.
I can’t find the dies or I would give them to the OP. I will take another look though.
Dave.