I ran my MK IV’s fairly hot , exclusively with 25 grainers, mostly Rem HP powerloct.
4198 sc could be pushed to 4100 in cooler temps, H335 god for just shy of 4000fps, may be best hot weather powder, shot a lot of Norma 200 also good for 4000 fps.
H322 was found to be way too temp sensitive, even the new stuff.
IMHO this thing comes alive between 3900-4000.
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