ORIGINAL: bronko22000
Who knows. And I don't know what they are doing to this new propellant to give these 'small' cases the same MV as the old reliables like the 338 Win Mag. and 300 Win Mag with similar pressures.
I think if they made this propellant available to the public you could probably get pertty close to these same ballistics out of your bolt action 308. Can you imagine something like a bolt action 358 win with this new powder. With - say - 25% increase in MV/Eng without any increase in pressure? That would be one heck of a round.
It has nothing to do with the powder. Let's take the 300WM vs 300 WSM for example. The 300WM loaded to SAAMI specs is usually loaded weak in factory loads. The rounds must work in any gun so the bullets are loaded deep into the case and use up powder capacity. I wring a lot more velocity from my 300WM than any factory load (nearly 3000 fps with a 200gr bullet) but my rounds would not fit in the chamber or mag of some guns.
Some of it has to do with the shorter geometry of the cases, they are slightly more efficient. Nothing you do to a 308 will make it into a 300 WSM. And few people are truly able to get the 300 WSM up to exactly the velocity of a regular 300WM, it's usually about 100 fps short.