They are alike in that regard. Solids require more pressure to engrave with the rifling, so the start pressure is higher.
I used QuickLOAD's default case capacity with the TTSX, specifically (the longest of the 8 different 140 grain Barnes bullets shown), I show 100% case fill of IMR 4831 weighing 52.1 grains with the COL at 3.330". That matches Phoron's experience. If I swap in H4831, I get 52 grains being 94% case fill. If I swap in H4831 SC, 52 grains shows as just 90.4% case fill. But despite the higher bulk density of the H versions, it also predicts lower pressure and velocity at 100% fill for them than for the IMR version. That's due mainly to the IMR version having a much larger progressivity factor (steeper initial burn curve) that makes it burn more efficiently in this particular application.
What COL did you end up loading to?
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