Latest development from a RUAG spokesman is as per below.
Only the chamber and of course the “cone” from the chamber (green section) into the rifling is different, but this is no problem cause your gunsmith has to cut this part anyway especially for you (green section).
So a complete barrel blank with only the rifling in 10,3mm (red section) without chamber would suit your needs, if your gunsmith is able to cut the chamber.
The 10,3x60R and 10,3x68Mag use also the same bullets.
The background of the development of the 10,3x68Mag was to use the already available rifling tools, barrel blanks and bullets of the 10,3x60R but to create a more powerful caliber with less bullet drop.
So this is why only the chamber eg, case of the 10,3x68Mag is different to the old 10,3x60R.
file:///C:/Users/jsg/Downloads/10-3-x-60R-en.pdf
file:///C:/Users/jsg/Downloads/10-3-x-68-mag-en.pdf