Might want to edit the title of your thread. Headspace refers to the fit of the cartridge in the chamber.
What you want to know is how to check the engagement of the bullet in the lead/rifling. Yes, that is a very tricky question since the geometry of the bullet tip impacts the measurement.
What many of us do is follow the recommendation of the bullet maker (berger has a reloading manual for example) and start at the recommended cartridge overall length. The bullet tips tend to be a bit inconsistent, but you do a bit of averaging and that gives you a seating depth that is reasonably consistent. Hopefully your seating die does not make contact with the bullet tip, or else you will have a bunch of problems ?
You try out that basic dimension to see how it works, and if you are not satisfied you load up groups of 3 to ever increasing length provided it still fits in your magazine and has enough neck engagement to be robust in handling. Steps of 0.020" are fine enough. Then go and fire off your 3 round groups and somewhere in there will be a batch that may be substantially better than the others. You might even need to try some loaded shorter than the recommended length, but if you do that watch carefully for pressure signs since you are reducing case capacity and pressure will go up.
David Tubb claims that he loads his match loads longer than the point it will engage the rifling and the bullet basically gets pushed back into the neck by the rifling so that the bullet is guaranteed to be jammed every time. I don't like the sounds of that, but then I'm not a match champion either, so apparently it works for him.. Not sure I would want to take loads like that into the field anyway because 95% of the time I don't get to fire a shot...
Bookmarks