No idea on 7977 but R33 should work as it does in the .257WM and .264 Win. It is closer to Retumbo than H1000.
R26 is almost the same as 7828 and the old slower lots of MRP. R26 gives me about 60 fps more in the 7RM than my old H870 load with 160s.
"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli
