Someone feel free to do the math behind me, but this is what I found;

A SMK 175 gr HPBT for .300WM, at a 1000 yds will have 1361 FPS with 719 FT-LBS, going subsonic at 1200 yds.

A SMK 175 gr HPBT for .308, at a 1000 yds will have 1185 FPS with 546 FT-LBS, going subsonic at 1100 yds.

It would take some radical load development to invest in a .300WM if I already owned a .308.