OP, read this? http://www.6mmhot.com/

Eddy, funny Rich at Sierra told me yesterday he is running a 6x47 and 22x47, latter 80/3600 and 1" on a good day at 600 yds, 2" any day, NOT bad. 3200/107 in the 6. No info given on Bbl length. For me I want no more than 24 on a hunting rifle for how I hunt so speeds may drop a little.