Dear mi-fordson:  This thread started getting scary when .308 Winchester Data began appearing.  Your query was about .30-40 cast bullet loads and increasing velocity for Deer Hunting.
  My old 1967 Lyman Manual gave data for Cast Bullet #311290 with Gas Check (#2 Alloy) and 2400 powder:  starting load 17 grains = vel. 1450 f.p.s. and  Maximum Load 22 grains = vel. 1725 f.p.s.
  Caution Caution - This is old data.  (There are also other powders that achieve higher velocities with lower pressure).  Always check current data and multiple sources.  I have not loaded or used cast bullet loads in my Krags.  But the Krag is famous as a fine cast bullet shooter.  (It is very important to know the actual bore diameter of your Krag's barrel).
  There is a Forum called "Cast Boolits".  If you have not checked it out, there is a wealth of information there.  Please always cross check loading data with multiple reliable sources.  Enjoy your Krag and know its limits.

mi-fordson:  you never indicated what charge weights of IM-4759 and #2400 you were using to get the velocities reported.  I'm also curious to know the alloy and lube you used and if there were any problems with leading?