Thanks for the reply. I was aware of the relationship of twist rate and bullet weight (a non stabilized bullet is an ugly thing). All other things being equal, (cardtridge, bullet, COL, primer, velocity) powder type is crucial. Nothing I've used beats IMR, and when I have called Remington, Spear, Sierra, Nosler, etc to pick their brains for an accuracy load, they have never recommended anything else.
The Bench Rest folks are like racers. They leave no stone unturned in the quest for better performance. Many conversations have turned to how many fairies can dance on a pin head I'm sure.
The Ballistic Coefficient (how well a bullet travels relative to the pull of gravity) also plays a role, but is far more important in rifle shooting than in pistol; most pistol bullets, especially the heavy hard cast semiwadcutters have the BC of a flying brick.
Simply stated, the ballistic coefficient is a measure of how well a projectile behaves in air. The ballistic coefficient is an important and useful concept that relates the drag deceleration of a given projectile to the drag deceleration of a standard bullet. The concept of the standard bullet and related ballistic coefficients was a major step forward, because otherwise the drag characteristic of every type of bullet fired would have to be measured individually – an impossible undertaking