Sounds like your minimum dimension chamber is doing great.
Plus the fact you're using Nosler brass, never used it myself but I speculate from the price of it, it should be good.
Another benefit is the cases 35* shoulder. I have noted over the years that the Ackley Improved cartridges (40* shoulders) tend to not stretch as much as their parent cartridge. While 35 is not 40* it is close and somewhat better than say a 20* shoulder. The .243Win has a 20* shoulder and the last one I owned shot lights out but I had to trim the brass every time seems.
I too have/shoot a 6.5-284Norma. Mine is a 112BVSS Savage and those velocities are about right. I shot the 120gn Ballistic Tip VERY accurately out to 500yds, pushed by 58.5gn of RL25 and BR2 primers, this load left at 3225fps and numerous times my groups were well under 2" @ 500yds.
Currently shooting the 140gn A-Max and accuracy is just as good. Using 59.0gn of Retumbo, again w/BR2's and velocity runs 3040fps.
All that to say, I am on my 5th firing with Lapua brass and have not had to trim yet. Had to FL re-size after the 3rd firing but still going strong. Love this round. JohnnyK.