You can get any blank then right? By definition a blank isn’t profiled or chambered for anything. Just get a 6mm blank in the length you want and go to town.
Any competent gunsmith can make an RPR barrel from any blank. Now if your Smith cant contour than that's the problem. I've never heard of an RPR blank.. RPR barrels are made from the same blanks as any other barrel.
Has anyone on here used a Preferred barrel blanks barrel on there rifle if so how did it shoot I'm looking gnat picking up a shouldered pre fit from them in the near future but cant seem to find any reviews on them.