This was discussed at length recently on another thread. The difficulties are.

1) Apparently the barrels are brazed together, so regulation for a different caliber will be a bitch.
2)Apparently it has been done into a 450#2, this is the lowest pressure of all the NE rounds. Nobody is prepared to commit to a higher pressure cartridge and nobody has built one because of point 1. Some got it to regulate others did not.
3) If you are going to the trouble there are better actions availible.

Regards