Any chance the drawing is for proposed changes that never made it into production? The radius on the outside is not on my barrels. I made a detailed drawing with lengths and diameters that was sent to Pacnor for making my barrel. The taper ended where the parallel 1 inch diameter started.
Looking at the SAAMI drawing of both the cartridge and chamber they have a .155 radius at the corner we have been discussing. I did not measure it on the 30/40 Remington cases on hand but it is there. That radius makes it much more difficult to see where that now theoretical line is (1.65/1.62).  Again on the SAAMI drawing neither worked out on the math.
All said and done the SAAMI specs do not have to match the original SA drawings or actual dimension of the finished product. Just safe in practice with most firearms manufactured. If the .030 difference is real could explain part of CoRofleMan's difficulty. Just hope his rifle was not reamed for 30-06 blanks.