Not going to say it's definitive but I was able to finally get decent groups with the 266469 in my 6.5CM last week. Went from patterns to groups once I slowed it down to 1600 - 1650fps. Heat treated Lyman #2, lubed, 16gr IMR4198 & A5744. 5744 was faster 1686 - 1695fps but tended to throw a flier, 4198, OTOH, was very consistent at 1614 - 1619fps.
I shot two groups with 5744 one put a cluster of 4 in .725" and tossed one outside for 1.765" the second 5 shot group was 1.461".
Shot 3 groups with 4198, 1.329", 1.334", & one with 4 in .732" and a flier that took it to 1.610".
This in 10 - 15mph swirling winds where the wind was at my back at the bench, 90deg to my left at 40yds, and in my face at 100yds.
The NOE 266-140 has been out of stock for months so have given up on getting one.