Mule Deer (John Barsness) listed H-4831 and RL-22 as the powders to try with 140 gr bullets for .260 Rem and 6.5x55 in his article "Update: Handloads That Work" in Handloader magazine Issue #231 (October-November 2004). You might try to find a copy of that article to see his load recommendations (powder weight).
For the experts, it might help if they knew what rifles (and barrels if not the factory barrels) you are using (could twist rate be a factor? - probably not, but might be a factor).
Might also help if people knew what type of bullets you had tried in the two weights.
