More slam to the gram!
The great advantage of the large case 300 mags (300 Win Mag and 300 H&H Mag) over the 30-06 is the ability to accommodate heavier bullets. Therefore, to get the full benefit of say a 300 Win Mag, use 200 gr bullets. Moving up from 180gr to 200grgives you an increase of 11% in bullet weight, meaning better penetration and less wind drift at extreme hunting distances on the plains, less meat damage up close, and uses less propellant (a little longer barrel life). Velocity is only down by about 4%!
In the field with larger animals the 200gr bullet will have more knock down power than a 180gr of the same make and model. This has been prooved in Africa in hunting and culling operations.
In his excellent book Rifles for Africa (p193) Gregor Woods states..." the only real justification for the small bore magnums (here referring to the 300 Win Mag and 300 Weatherby Mag) is their ability to shoot heavier bullets at useful velocities for long range hunting." Further on he states..." the hunter should be using 220gr bullets, or at least the lightest, 200gr bullets in the magnums". This was with reference to bullets containing lead cores. In monometal, with a barrel twist of 1:10 inch, 180 -200gr would work well.
Emperical research done by Dr Kevin Robertson, a well educated and published Professional hunter, veterinary surgeon and sports hunter, has found that the heavy 380gr Rhino bullets in the 375 H&H gives stopping power which is similar to, or exceeds the 416 calibres when used with solids on buffalo culling in Africa (416 Rem Mag and 416 Rigby).
"More slam to the gram, and more bounse to the ounce" !!!
Hope this helps