For 600 yards you should be using 139 gr scenars.
I have tried 139 Scenars, 140's, and I believe 142's
I have tried all the 130's just about, Bergers being the best 130.
For some reason, I could never find a heavy bullet I was satisfied with and had plently of help from everyone here and one other board. Erik Cortina was a great help!
I talked to one other person who's 6.5x47L loved 123 Scenars even out to 1k yds. that's all he shoot out of his gun. He also stated his gun didn't like heavy bullets.
Now you put 120smk's or 123 Scenars in my gun, and it will plain shoot! It was again proven this last Thursday as I was outshooting several good shooters with my gun and the 123's. After the third string, they actually came to me and wanted to know what I was shooting. I was "very" windy during our practice.
The barrel on my gun doesn't like high pressure with the heavy bullets, but you put 39.3 grns of RL15 behind a 120smk, it will just enlarge one hole with 5 shots! NO pressure signs!
IN fact, I spoke with two other who stated the same thing as I am stating. They were going to sell their guns, but they were so accurate with the smaller bullets, they kept them. I shoot with a person who's gun likes 140's, but he is also shooting 123's now and his gun will also shoot them as good as the 140's.
There were many post about 2 years ago now concerning this! Anyway, I am happy with it! there is also a post on gun week on 6mmbr, a person won a match shooting 120smk's with his 6.5x47L. I havn't read it in awhile, I might look it up and see if anything has changed!
This article help tremendously!
http://www.6mmbr.com/gunweek072.html