I've run two different .300 BO's - one a CMMG, and the other a Daniel. Both worked flawlessly with subs or Supers, although the CMMG was not terribly accurate - about 1.5 to 2 MOA with handloads.

I'm thinking there is some other issue with the gun in question, as it should work well with either load.

"...the designer of the .270 Ingwe cartridge!..."