How much does one complete rotation of the bullet seating stem on a RCBS bullet seating die change the bullet seating depth ?

On a Hornady die ?

Hammer

it depends on the bullet!

Figure it out yourself:

1" Divided by # of TPI on rod.

Hammer
Do like I just did!

Measure (with your caliper) the length of the die, then turn the seating stem either in or out one turn and measure it again! Now, subtract the lower number from the higher!

Mine, for example was a 221 Rem Fireball!
1st measurement 3.216
2nd measurement 3.182
the difference .034
So, the bullet seating depth would change 34/1000 inches!

If you set your die up with a particular bullet, it will change depth exactly the same as the change in the seating stem!

My calculations show between 35 and 36/1000ths. My skill at measuring is not as refined as yours.

Hammer