I've shot new manufacture Wildcat bullets, a couple of years ago in NV that patterned better than 8" @ 20 yards. That's a one shot pattern.
I've killed 3 chronys but it was my fault every time.
I've weighed and sorted winmag's LRABs. Their baring surface seems to be about 0.10" shorter than the 150 Bergers so I'll start out with the COAL that the seating die is already set at (same setting for 150 berger and 169.5 WC)
The initial powder charge will be 82 grains of 7828ssc which pushed the 150 Berger to right at 3500 and sub 1/2 MOA @ 200 yds.
This barrel, the second one on this action, from DerekM in Ohio, is 2" shorter and lighter contour than the original.
Differences between this barrel and possible different throat than the original barrel are:
New barrel shoots Bergers very well @ 3500. Original barrel shot the same Bergers in large banana shaped groups.
This barrel though 2" shorter produces same velocities with same charges as the original 30" barrel.
New barrel is just as accurate as the shot out original was in its hay day.
I called off my trip to the hills to tune up for going a mile with the 375 to work on this project.
Should be a fun day.