Hornady oal gauge.. case headspace difference questions..

[PlinkIt]

Ok I bought the Hornady OAL gauge seemed like a legitimate set up but after playing with it I have an issue with the way this works..

the MODIFIED case as they call it is simply a a case drilled out and threaded.. so the case will rest on the taper of the case when pushed into the barrel while checking for correct bullet seating depth.. so it would seem that what you really get is a correct distance from the shoulder of the case to the lands.. not from the bolt face to the lands.. so now the headspace for this case is measuring 1.458.. now my fired cases are measuring at 1.461 headspace.. considering that the gauge is being pushed and held into place while you check the bullet seating would I not be correct in thinking you will need to add this difference on head space to the OAL of the cartridge to be loaded to the lands?..

Put all of my notes from this evening on here and compared them to a loaded Winchester Match round with the same bullet

Headspace
1.458 Hornady MODIFIED case for OAL gauge
1.461 fired case from rifle
1.455 Winchester Match with 69gr SMK

OGive
1.891 Hornady MODIFIED case with 69gr SMK (have not added the .003 for the difference in headspace)
1.865 Winchester Match with 69gr SMK

OAL
2.278 Hornady MODIFIED case and 69gr SMK (have not added the .003 for the difference in headspace)
2.250 Winchester Match with 69gr SMK