I have two 6mm Creeds, one with a 22" barrel and one with a 16'5" barrel, both 1-8" twist. I have found that I lose almost exactly 200fps across the board on the shortie with same bullets it doesn't matter which powder I use. I get excellent accuracy on the shortie out to 600 yds, which is the longest range I have had access to. I am currently building a 22 Creed.