Let's talk TRANSONIC!

[Don McDowell]

I think one of the most interesting things to ponder on this is the 223/5.56. If you look at how far things have progressed with that cartridge and twists, it makes for a pretty good source of information.
The original 12 and 14 twist wouldn't stabilize a bullet heavier than 55 grains, but as they have increased the rifling twist, that cartridge now will rival the 6mm's at distance.
The problem we have with these big ol chunks of lead, and blackpowder is the lack of velocity to take full advantage of faster twists and heavier bullets.