I shoot a little tighter groups at 100 yards with the 55 gr bullets but that could just be in the head. I shoot a lot of the 75 gr HPBT Hornady match bullets CCI 400 primers around 23 gr IMR 8208 XBR have shot many sub MOA groups at 400 yards with that load but they are not as tight at 100 yards as the 55 gr vmax tend to be but the 55 gr fall apart at 400 yards with the wind kicking them around. I'm in the process of building an AR-10 in 6.5 creedmoor just got the Krieger 26" barrel with headspaced bolt from Fulton Armory the other day absolutely cann't wait to get it assembled and try it at 1000 yards after some load devepment. On this build I am seriously considering using Locktite 620 between the upper reciever and barrel extension because my fit is a little looser than any of my other builds have been most of my 223 fits have been a nice snug fit with no barrel nut installed this one has a couple thousands play I even looked on Brownells to see if the had a upper reciever lapping kit like they do for the AR15's. Crazy what we will do chasing that last little bit of accuracy out of these guns but that's half the fun.
when I used to shoot 100yd benchrest we all used 52 to 55 grain bullets but we used 1:12 twist. That was before 6mm took over.
I have 1:7.7 twist. I have a bunch of berger and sierra flat based 52 to 55 gr bullet that I shoot from time to time but they really need a slower twist barrel. a 1:9 even would be better.
I really want this one for reaching out to the limits of .223. Maybe one day.
as far as the long range boatail match Mk and VLD's and such grouping better at 200 than 100. Doesn't seem feasible for a bullet to have that much yaw at 100 and stabilize out there about 200 or 300. The physics just baffles me
Now I can see that with these new high powered scopes you could actually have a more precise aiming point at these longer ranges. that would make it a lower MOA group. Say 3" group at three hundred yards is 1 MOA. With a more precise bulls eye and a high magnification scope you might do better at longer range.