I was able to shoot one of my tightest groups ever with RE26 & a 142 SMK from my Creedmoor. 3-shot group went into a perfect triangle measuring .41" at 400yds.
I worked up to 46.9g RL26 in my Tikka with the 147's, but I've got the seated out to almost max mag box length, in which the Tikka is very generous. It's not a compressed load with them seated like that.
I get nearly identical results with RE 16 and 26 in my 6.5 CM. If anything, slightly better accuracy with RE 16 so tend to use that and save the 26 for other cartridges.
That's all I've tried in mine, I get 2930 FPS and dime sized groups out of my 27 inch Brux barrel at 100 yards. I took 3 deer with it last fall, all DRT.