The best solution for .500 3-1/4" brass is to blow out .470 NE brass. I have used 11 grains of Red Dot, fill with Cream of Wheat and plug with a small wad of newspaper or other paper. Bullseye or Unique would do just fine too. Shoot them in the back yard like dry-fire practice. Viola! You have .500 3-1/4" brass.

Check with Ken at Kebco for once-fired .470 brass: Classified listing in Nitro Express classifieds.

Curl