Why does HAP and XTP bullets reach such high pressure at low charge weights with low velocity compared to bullets like the Golden Saber or Gold Dot HP? Here is some data from Accurate and data from Hodgdon shows the same theme.
Ramshot ZIP
124 HDY XTP 3.3 888 3.7 967 34,893 1.060
124 MIL FMJ 3.8 879 4.3 985 34,750 1.100
124 REM GS 4.1 970 4.6 1,055 34,880 1.145
124 SPEER GDHP 3.8 888 4.2 979 34,218 1.105
Accurate #2
124 HDY XTP 3.3 877 3.6 938 34,518 1.060
124 REM GS 4.3 989 4.8 1,054 34,859 1.145
124 SPEER GDHP 3.9 917 4.3 989 34,347 1.105
124 WIN FMJ 3.6 880 4.2 992 34,675 1.100