HI PAT...I think you are asking about a 6mmBR with an 8' twist bbl....,,it culd be some other 6mm chambering,,,if so please correct me))...I have shot one for 3yrs now and it has been one of the best combination of cal.--chambering--twist--etc.. that I have ever encountered.....
For pure varmint use,,I would use Hornaday V-max bullets...,lil ones to get the good splat factor) of 65-75-87gr varieties....or...Sierra 60 or 75 gr varmint bullets ....these have proven to be very accurate and dont cost as much as the hard to get "true" benchrest bullets....,,save the custom "botique" bullets for the real deal...
I found 133-322-530 to work great with the bullets of 70gr or LESS and 4895 or Rx-15 with the bullets of 75 or larger,,I usually use powder charges near max and jam the bullet aprox .007-.010" into the lands to work best for me..
Since you asked for a specific load...CAUTION!! Here is one that works for me in ""MY"" gun....34gr Rx-15--Sierra 75gr varmint bullet,,,of course seating depth must be adjusted for your specific chamber and the ammount of freebore it has...and dont forget to try Winchester WSR primers...I found them to work just as good as the Fed 205's that are so popular...as far as the perfect powder...I think it is Rx-15,,some will disagree))..I can adjust the powder cahrge up or down to suit the entire rage of 6mm bullets,,from 60 to 107gr)) with great velocity and accuracy,in my 28" barrels...,,Roger