Determining Maximum Powder Charge

[Jamie]

However, with a bottleneck rifle case, thanks to the relatively slow powders in use, the high engraving force that causes the greatest pressure rise and the relatively small reduction in case capacity from seating the bullet deeper, the pressure increase from seating deeper is usually more than offset by the decrease in engraving force (thanks to extra bullet inertia from the "running start" the bullet gets on the lands) and the net result is pressure decreasing as you move farther from the lands. You will eventually reach a point where the extra freebore doesn't help anymore and the reduction in volume takes over.

Isn't that what I said? Close to the lands it could help far from the lands it wouldn't and reducing COAL increases pressure.

Don't underestimate the pressure increase from reducing case capacity. It only takes 1 grain of powder to go from safe to stuck bolt.