My experience with the 25-06. The 25-06 is considered an overbore cartridge. Meaning the case is oversized for the size of the bore. Until lately there has been no powders that would bring out the full potential of this cartridge. Same for the big Weatherby Cartridges. OK, there has been powders that worked and gave good accuracy, but they did not develop the full potential of this case.
Now that Hodgdon has came out with a new batch of powders, this cartridge can reach it's full potential. I chose RETUMBO for several reasons. 1. Temp swings, Retumbo was designed to prevent velocity swings due to temp extreames. 2. Retumbo gives me the highest velocities from the 25-06 using the 110gr Nosler Accubond. A moderate charge of Retumbo powder, gives me the same velocities as higher loads of other powders, with lower pressures.
The snow test. Take your regular load and shoot from the prone position, then go out and look for unburned powder in front of the shooting position. Retumbo leaves no unburned powder from the 26" barrel.
Just my 2 cents. Rog