[threetango]

AKA, THE 257 Wildcat.

https://www.outdoorhub.com/how-to/2017/03/06/introducing-new-257-wildcat-cartridge-2fity-hillbilly/

 

[SHOOTER13]

Not too much into wildcat cartridges...

Chances are it has a close twin that is mass produced...or I just don't need it anyway.

Thanks for the link Top...