Re: best powder for 150&160 7MM STW
I shot a Sendero SF in 7mm STW for a while. I never was able to get good accuracy with 150s. I don't think I could find a powder that was really right for them. H1000 looked good on paper but never proved up. At the time RL22 was hard to get here, 25 and Retumbo weren't on the market yet.
I had really really excellent luck with IMR 7828 with mollied 120 grain Noslers, I want to say 83 grains but that's from memory, and it did pretty fair with 140 partitions. For 160s, I shot mollied partitions over 87 grains of H5010. Either the 120 or the 160 would shoot .75" at 200 yards and have the same POI at that range. Handy. :-)
Flex is for people who don't have lockers.