Thread: Seating depth difference.

Get a bullet comparator and attach it to your vernier. In a pinch you can epoxy some nuts together.

Measure the projectiles from base to ogive. Then measure a loaded round from case base to ogive. Now you can work out how much of the projectiles bearing surface is held inside the case.

Seating the base of the projectile further down will cause more pressure...smaller expansion chamber. Seating the ogive too far forward will also cause higher pressure when you start "jaming" into the lands.

The way I do this is to use the hornady tool and modified case to find the lands in the chamber for a particular projectile, and then load 10 thou back, unless there is a specific reason not to (vld projectiles, or fine tuning group size).