Is 60.4 your max for this bullet choice? It looks like 60.0 and 60.4 have the same elevation and windage, with jus a very slight shift compared to 59.6. Maybe 60.0 is the sweet spot in that node. Idk, I hardly even shoot anymore.
I use the 0.375 insert for 6.5 CM and 6.5x47L. I only bump 0.001", but I don't compete (thankfully... I'd perpetually get my ass handed to me), and my round count is low enough a few heavy bolt closes isn't going to hurt my enjoyment of a rifle, or wear the lugs out. Shorter cases after firing can be normal. I'd question your powder choice for 140 class projectiles, but it is hard times, and H4350 might be difficult to come by. Either way, I'd still suggest any of the powders in the IMR 4451, RL-16 or 17, H4350, etc., for ANY bullet you'd shoot in the 6.5 CM. You will get as good, or better, velocity with them than a powder you would normally use in the 223 or 308 WIN.
Gonna go shoot my targets for score after looking at a house. Maybe we need a 100 yard standing as well. I don't think it's fair to lump 100 yard groups in with the 300 yard groups. Less environmental factors to consider. My 6.5x47 Lapua target will have one sighter, and 8 shots each for the three targets since I only had 25 clean pieces of brass ready to go. I'll finally be able to process my 300 pieces after this session. My 223 target will have the required number of shots though. Should be good times!
I wouldn't get hung up on a factory projectile that shoots well in your rifle. There are plenty of offerings out there that are great hunting projectiles that can be tuned to shoot as well, or better, than the factory ammo you are interested in. That said, before I got into reloading, one of the most accurate rounds I found for my Ruger American 308 was the Federal Deer Thugs 165 flat base, which is the Speer hot core as well. It had a protected soft point like the 140 you're talking about. I never found any available to buy though, so I just went with Sierra and Berger for hunting projectiles and did not feel like I was missing out on any accuracy or performance at all.
The only thing holding me back from getting a larger case for the 6.5 is just barrel life. I have this mental block against anything I see as being much more overbore than the Creed. 7mm08 is just about perfect for performance and barrel life imo. Now, if we could just get some straight wall precision rifle cartridge development, that would be amazing!
I think the lights will group with the lights and the heavies will group with the heavies.
I think a fair test would be 3 each: Lights Heavies Middles Then one set of 3 with a light a heavy and a middle.
That should tell if it's worth worrying about. Personally for competition I'll probably sort them all anyway as a failsafe to catch any way off the mean. I binned them right back in the regular flats in .02g bunches.
I think you'd need a larger sample size of each to be absolutely sure. At least from my perspective, and how much I personally influence group size just by being behind the trigger. You might be able to determine the effect, but I'd be comfortable only with a larger aggregate.