Also, try a seating depth test first.
Charge a few cases with a light powder charge like 39 grains. Then seat bullets at jump .010, .040, .070 and .100 or start at mag length and shorten them by .030, .060, .090, .120
Shoot these at 100 yards to find the best seating depth.
Then load your charges at 42.8, 43, 43.2, 43.4, 43.6, 43.8
Fire those either at long range for a ladder or load three of each and fire them slowly at 100 yards, keeping the barrel cool. After this you will have a load.
Thin barrels typically have small nodes and need to stay cool in my experience, but they can be very accurate.
