Seating Depth
How deep the bullet sits in the case neck, set by overall length or base-to-ogive, and one of the most powerful accuracy tuning variables a handloader controls.
Seating depth is the distance the bullet is pressed into the case, which in turn fixes the cartridge overall length and, more precisely, the base-to-ogive measurement. It governs how far the bullet must travel before it meets the rifling, and small changes of a few thousandths can tighten or open a group noticeably. Because of that sensitivity, depth is a primary lever in load tuning rather than a fixed value.
The right depth depends on the rifle’s throat and the bullet’s shape, so what shoots well in one barrel may not transfer to another. Handloaders typically find a working charge first, then walk the seating depth in steps to locate the spot where the rifle settles, adjusting the bullet jump toward or away from the lands. Recording the base-to-ogive number, not just overall length, keeps the result repeatable across bullet lots.