When the .300 Win Mag was popular in high power rifle long range matches, Sierra HPMK's of 190 and 200 grains were favorites. Seated in new (or proper full length sized) cases with IMR4350, charge weights in order were 71 and 70 grains as I remember. Standard primers gave better accuracy than magnum ones. 1:12 twists were favored in the 28 to 30 inch barrels used.
The 230 gr Berger OTM and the 225 gr Hornady BTHP (at 1/3 the price) both give excellent accuracy with high BC's in my 300 WM using both H1000 and Retumbo.
I also hear good long range accuracy reports on the 208 Hornady AMAX.
There are some very favorable reports here on the 230 OTM and 208 AMAX for long range hunting though I haven't tried them myself yet.
208 Amax and 76-78 grains of H-1000. This will put you about 2850-2950 depending on barrel length. You will be good for everything from roaches to rackzilla.
Factory Remington 26" Model 700 300 Win Mag, 73.0 grains H4831SC, Remington brass, CCI250 and Berger 215 Hybrids with an outstanding B/C of .696. In this rifle these are running 2,867 fps with ES inside 10 fps. Be carefull, this is a warm load but safe in this rifle, it may be too hot for yours so work up.
COAL is 3.678". This is .020" jump. It was nice because this is the most accurate seating depth we found and it just fits in my friend's factory magazine with enough clearance to feed fine.