Thread: Minimium amount the projectile should be seated inside the neck of the case

Marty's quite right. You need some neck tension to control the angle of the seated projectile. If you seat very shallow into the case, you also run the risk of the projectile jamming in the lands. This becomes a major problem when you go to uncock and remove the unfired round from the chamber, only to find that the projectile is still jammed, and your action is full of powder.
If youre determined by magazine length then thats the maximum depth. You can always seat deeper from that point.
10 thou is a good starting point, deepening to 15 thou and even 20 thou.
If youre not limited by magazine length, then start with just touching the lands and move deeper to tighten up the groups.
Changing powder loads usually results in vertical variation
Seating depth changes usually show up in the form of horizontal variation