If you read that a certain load develops 39,600 CUP, you should not think of that as anything but a general indicator of results that might be expected.  Any time you change anything in a given load, you will potentially change the pressure that load develops.  If you change primers, pressures will change.  They will increase if a hotter primer is used and decrease if milder brand is used.  And there is variability in primers from a single source.  I would expect a tough bullet like a Nosler to offer more resistance to the rifling, and to develop higher pressure than the same weight Sierra Matchking.  Use your micrometers.  Not all .30 caliber bullets are .308 diameter.  And slug the barrel of your Krag.  They run from about .306 to over .311.  If you shoot a .308 bullet in a .307 barrel, pressures will go up.  If you shoot a .308 bullet in a .311 barrel, pressures will go down.

Powder changes from one lot to another.  Not much, but there are changes.  Brass changes from one maker to the next and may change with the same maker from lot to lot.  Compare the volume of W-W cases with R-P cases.  Weigh both types.  There are many reasons to stay away from high end loads for your Krag.  There are not too many good reasons to use them.