So yours wouldn't shoot the 115s either?
I put together a 20 lb heavy varmint 30" 6-284 with a bartlein 5R 1 in 7.5 twist. Tried to get the 115 DTACs to shoot but finally gave up and went to the 107s. The sierras shoot fine. I know I am not maxing out the velocity but at 3265 but I cannot complain. Barrel life is precious with this chambering so I stopped when I got excellent accuracy.
Unfortunately my rig is a single shot arrangment as it is a SA Rem 700.
Always good to hear of others experiences.
