When I worked up that 165/3,300fps load, I was using one of those "One Book - One Caliber" load manuals for the .300WinMag. It was from the mid-90's. I'm looking at it right now and the Speer load data, which was fired in a 24" Ruger M77, went up to 83.0gr of 7828 for 3,280fps. I was shooting a 26" barrel and got 3,300fps with 81gr, so I stopped there. I also shot 80gr with 168's and made 3,250fps. In that manual, Speer said their loads did not exceed 54,000cup, so I'm assuming they tested them.
Regardless of 50fps here or there, the 300WinMag does bring a lot of juice to the table when loaded to its full potential.
