IMO you are doing a great disservice to your 300 mag when you settle for using less than a .630 BC bullet, especially at long range. The 300 Win. has the capability to fire heavier bullets fast enough to get the full benefit of the high BC of the heavies. The average 180-190 grain bullet carries around a .500-.550 BC, which at one time wasn't bad, but you have many more options to utilize the the cartridge for what it was intended for and that is to carry energy to greater distances than cartridges like the 30/06.
Although you can be effective with the 168-190 grain loads at higher velocity, in most cases the average hunting bullet pales in comparison to high BC bullets in the 300 mags due to two extremely important benefits #1 wind resistance and #2 energy delivery.
For long range shooting BC is king for several reasons. Although, your muzzle velocity will be lower with most high BC bullets because of the heavier weight associated with them your downrange energy, and wind bucking ability will more than make up for the lack of velocity.
For instance, let's look at the average 180 .505 BC fired at a velocity of 3100 fps, elevation 5000 ft, at 700 yards distance, retained velocity = 2115 fps, and energy at 1788 ft lbs, wind drift with 10 mph full value wind = 3.50 MOA or 26.2 inches
Now take a look at a high BC Berger 215 hybrid, .696 BC at 2850 fps, 5000 ft, 700 yards, retained velocity= 2133 fps, and energy of 2172 ft/lbs, wind drift with 10 mph full value wind = 2.75 MOA or 20.3 inches
And this is only at 700 yards, the numbers and benefits only get better the further out you get.