I have a .310 lube sizer die and have tried various cast bullets at that diameter but that don't hold a group like when the same bullets are sized at .312.  My bore shines and is in excellent condition, but must have been on Springfield Armory's .310 diameter groove day. 
I've shot loads with 10 or 12 grains on Unique for 100 yard CMP matches, but find Unique position sensitive which makes for vertical stringing during the rapid fire strings.  Harris was correct in that I see no stringing with Alliant 2400 powder.  It doesn't appear to be position sensitive..even with the light 16 grain charge.
I also cast for the Lyman 311284 very old traditional bullet for the Krag, but the 314299 bullet shoots better groups for me.

David, Give cast bullets a try in your Krag.  If you haven't read Ed Harris about cast bullet loads I'll find his artical (s) and post a link.  His basic 200 yard target load involves about any cast bullet and 16 grains on Alliant 2400 powder.  I've found that load to be very accurate at 200 yards.