Mixing Powders

[L Cazador]

The finicky part about reloading any caliber is the bullet. Berger has had so many complaints about their VLD (secant ogive) bullets that they have gone to a more reloader friendly hybrid ogive, a combination of a tangent ogive and secant ogive. Hornady is soon to follow as their ELD bullets can be hard to tune. That extra ballistic coefficient advantage doesn't matter when your can't achieve a consistent group or hit what you're shooting at! My two centavos!

[MT_Sourdough]

Most reloaders know this already.   I feel it still imperative to state that, before you try achieving factory load velocities, I'd recommend you chrony those factory loads. That way you'll discover real world velocity for that load in the rifle you are shooting.  Disparities between claimed velocities versus real world results can be quite extreme,

[recurveman]

The advantage that might be obtained for the average hunter is little to none.   Keep in mind that as hunters we are looking for "minute of deer" and don't have to shoot .25" groups.   Also everyone gets all fired up about cartridge selection.   Manufacturers make new cartridges so you will buy a new rifle.   The .308 (from a hunters perspective) will do everything a 7mm-08, 6.5 CM, .243, ect will do.   There is little difference between them.   When you look at it from the standpoint of a chuck of lead going through the air at a certain velocity there is little to no difference in practical hunting applications.    Even when you go from a .243 to a 300 win mag the only real difference is the energy.   The trajectory is very, very close and the energy really only matters if the bullet doesn't leave the animal.   If the bullet passes through then the extra energy really wasn't used on the animal.   

To answer your original question.    DON'T MIX POWDERS!!!!!!!!!