I have the Ruger Hunter in the regular grip with a 2x6 Simmons on mine. I have been shooting the Beartooth 300 grn WFN Gas Check bullets with 21 grn of H110. I never got any groups like yours and have been wondering if I needed to go up in bullet weight or shape. I'm going to try and find some bullets in 350grn something like the ones you are making and try them. I know the gun should shoot better. Thanks for the info on your loads.
Mike