Back in the '50's I had a rimmed 250-3000 Savage built on a High Wall Winchester, and formed the cases out of Norma 8X57R brass. The .444 wasn't an option at that time.

I now have a BRNO 21F in 6.5X57, which I load for using 7X57 brass neck turned to assure clearance. I would think that 7X57R S&B brass would be a logical source for 6.5X57R brass.

I warmly second everyone else's comments about the Meisterstück this whole process, from concept to reality, represents. Congratulations!