New To Reloading Question

[300BLK]

I would try either 29.0 or 30.0 and change seating depth to tune to your rifle.

Do you know how much jump you have at that OAL?

The difference between my chamber measurement and the OAL of the H 105 BTHP I loaded is .0205. I'm new to all these different measurements so is that sounding about right for the jump to the rifling?

Are you indicating 20 thousandths or 205 thousandths?  The former is reasonable, and the latter seems ridiculous.