If you want a .50 in Kali you don't need to move, you can buy a .50 DTC right now. It uses all the same components as the .50 BMG, what you need to do is fireform the brass after trimming 100th of an inch off. The Barrett .416 is a single shot M99 that has been rechambered from .50 BMG. Currently I haven't heard of them chambering any other rifles for .416.
Other then Barrett for a mag fed is EDM ARMS, McBros/McMillan, COBB Mfg., Anzio, Christensen Arms, Robar and VM Hy-Tech. Kali only bans detachable mags that are over 10 rounds and on semi-auto rifles.
There's also the .50 spotter/tracer that's legal as long as it's loaded with ball, AP or some kind of match round. Maybe some enterprising Kali person will neck the .416 Barrett back up to .50 and give us another choice.