The .505 Barnes Supreme has been around for quite a while. A Hungarian chap in Vancouver BC area thought he'd developed his own .50 cal. using a full length .460 WTBY case. I guess he didn't know about the .505 Barnes.

I fired one round out of it, his load IIRC was 125gr. of IMR3031 with a 600gr. Barnes for something over or around 2,600fps. Too much recoil for his skinny lad(back then). Shooting it was not fun.
I paid him $100.00 for the .375 H&H BRNO barrel he removed, unfired, from the ZKK 602 action he purchased for his 'wildcat'.

Huvius - the ctg. bullet deal is fun!