I be curious to see if you got the same results as I did when I stretched that partition out to 300yds. I was turning in phenomenal groups at 100yds. I was 98% set on using that load for my sheep hunt. Then I shot it out to 300 yds and good lord wasn't even MOA. I switched to 145 ELD-X and shot it out to 300yds and held MOA all day. I wish I could find that target. I was pretty proud of myself, the 150 sierras shot real too out to 300yds.
We saw something similar with the 150gr Partition in my buddy's 7RM T3. Great groups at 100, but at medium range it fell apart. We've been doing 10 shot groups at 100 for several years, to prove a new load or new rifle/scope/shooter system, and this situation was no different. Everything seemed fine at 100. Switched to the 168 Berger and it's been lights out to 600.
I had the 140 BTHP shoot to 500 well in one 270, but at 800 it had a lot more drop than predicted. That same rifle shot the 140 NAB out to 800 well, and matched JBM.
Never did figure out the root cause of those issues. And didn't care to. We just moved on.
