Originally Posted by boomtube
The ONLY way to learn the best seating depth for your rifle is to experiment with it. There are no secret ways to do anything.
Right. Years ago some benchrest shooters who set up a 100 yrd range inside a warehouse (in St. Louis, as I recall) found best accuracy with lands just engraving the bullet. Anyway, that's a starting point.
Polish dummy round bullet with 4-0 steel wool between various depth settings, and record length of engraved mark.
Five rounds each at various settings (on an off lands) should indicate a "sweet spot" for that particular load/rifle.
Caveat: don't set out so far that (1) the bullet sticks in lands and is pulled from the case when cartridge is extracted (this yields receiver full of powder and much cursing). (2) make sure your reloaded cartridge is not too long for the magazine box.