just for grins
no mater how you look at the results the 300 has a minor advantage in both retained energy and trajectory
lets compare the 212 grain 30 cal, pushed at 2900 fps out of a 300 wm
https://www.hornady.com/bullets/rifl...12-gr-eld-x#!/ (bc 673)
to a 175 grain at 2800 fps
https://www.hornady.com/bullets/rifl...75-gr-eld-x#!/ (BC 689)
about 2" flatter trajectory and 500 additional ft lbs of energy for the 300 mag at 500 yards seems to me to hold an advantage