Yeah, I'm not really sure what to make of the "fast barrel", "slow barrel" thing... for sure, new powder technologies can increase velocities without excess pressure. OTOH, when guys are getting a solid 100 - 150 fps over what the books list with standard powders and identical book charges, my gut tells me there's no free lunch. Pressure = velocity.
But I'm not an engineer and have no way of being definitive about it.
