I could not get speed out of Retumbo or Ramshot Magnum with a 130 gr Swift Scirocco, it did not seem to matter how much I dropped, I could not get faster than 3150 out of my 26" Pre 64 model 70. I gave Accurate Magpro a try, and hit 3250 with good accuracy and no pressure signs. I know it doesn't help that much with 140 gr work up, but Magpro might be a good powder to try.
