This has been my experience with a Win Model 70 26" 7mm Rem Mag. This was using the 168 LRAB and starting with IMR7977 as the owner wanted to try IMR. Reached max pressures at around 2900fps. Could not get LRAB to shoot under 1.5MOA at any seating depth. Slowly dropped charge to 2800fps range and groups did not improve. I did not feel anything below 2800fps was acceptable.
I got a wild hair and grabbed some of my RL33. I performed a pressure test starting with 75 grains working up to 79 in 1 grain increments. Primer is CCI250.
Here are the results:
75=2,962fps
76=3,003fps
77=3,023fps
78=3,108fps max load (slight cratering, easy extraction)
79=3,115fps
I did have to seat bullet out to just touch rifling in order to fit all of this powder in the case. Max COAL is 3.471". To aid in bullet seating I placed charged cases on my tumbler to thoroughly work powder down into the case before seating the bullet. It takes extra time but allowed bullet seating without crunching/compressing powder.
I loaded a few at 78 grains and discovered an average velocity of 3100fps, less than .5MOA vertical dispersion, low ES under 15 and groups inside .5MOA to 500 yards. Took it to 1,110 yards and groups opened slightly to .75-1.0MOA. I believe this is due to inconsistencies with the bullets and B/C, not a load issue.
Needless to say, the customer was thrilled with this out of a stock rifle.