I thought anything larger than .500 was illegal..510 seems to be the standard 50 cal bullet. Unless you are required to hav .500 or less, why y
would you build a special rifle to use non-standard dia bullet. I assume you would make cases from .348 win brass?
I've shot the 50 Alaskan. Nice rifle but with a tubular mag, and high recoil one would not use pointed bullets so BC is limited. I've lived with flat nose bullets in my M71 .348 too long.