That 200gr XTP/6.4gr W231 load was likely not more that 12,300 psi (in a 36,000 psi gun) and drundling along at 970 fps or so.
Your suggested 8.0gr/W231 would kick it up to ~18,00psi (in that 36ksi gun) and hit 1,120.
( . . . a reasonably pleasant plinking load for Dirty Harry.
)