where are the lands on this diagram?

[Hotolds442]

I think what he wants to know is how far into the chamber namely the throat do the lands and grooves begin. 2.8108 looks about right. Even though there is a short taper the lands will start to engrave lightly at that point.

Fixed it for ya.

ETA: I question the accuracy of that print. Points U and V, as drawn, cannot be the same measurement.