Re: How to figure Bullet seating depth
This is going to sound rough but has worked for me...
Size a case.
Seat a bullet way long past specs, like .100"
Record Cartridge Over All Length.
Chamber the "dummy round".
Measure the "dummy round" again, record length. (chambering should push the bullet into the case some.)
Using the inside part of the calipers, measure the marks left by the rifling to the case mouth.
The difference between Chambered COAL and the marks on the bullet from the rifling give you where the rifling starts.
Subtract another (.020"?) whatever you want to seat the bullet from the lands.
Hope that made sense.
So to answer your question, my "tool" that I use is a "dummy round".
Another tool to get for the calipers in the Ogive attachment. This lets you consistently measure COAL from the Ogive of the bullet. Instead of the tip of the bullet which is inconsistent.