Loks like you found a great powder charge with a low e/s Now to fine tune it do a seating depth test until you find a depth that will put the bullets in the same hole at 100yds.
I initially do two shots at each seating depth until I find one that puts two bullets in nearly the exact same hole, not just touching. when i find the best seating depth then I shoot them at 600yds and see what I get. I always get the e/s down and at 6fps it looks great for you and you shouldn't get much vertical at long range.
Here's a link to a group I shot with my 338 Lapua AI.
265gr HAT Group