It is not that they can't rebore and do riflling for that this caliber, it is the cost of deep hole drills, rough and finish bore reamers, cutters and chamber reamers etc that need to be invested in for a very limited market, where the bases are covered by 338, 358 and 375 calibers.
Ruger has anounced a #1 in 9.3x74R but has yet made one. It has bee anounced for a long time. I believe they are waiting for feed back from dealers to find out how much interest there is for this caliber, before the gear up and make them???
I ask about that rifle, and all I got is a shrug of the shoulder, if it ever it is made I might buy one. Not that I ever would need it but it would establish bragging rights.
In a #1 it is a beauty.