Have a Krag that I have fired 180 grain FMJ through using 33 grains of IMR4894 and have had excellent results.  Consistently can put 5 rounds into 2.5" at 100 yards. :) My bore measures .309".
Wanted to try cast loads, so i loaded up some Lee 200 grain gas checks that cast to .311" which I sized to .310".  The "nose" or main part of the bullet would not slide into my muzzle, so I figured that this bullet was a good fit since the nose should ride on the lands and the base which was .001" larger than the bore would then fill the bore. 
Used liquid alox as lube, installed gas checks, loaded to the correct length, and then loaded with 33, 34, and 35 grains of 4895.
Could not put 5 rounds onto an 11x17" target at 50yds. from a rest. :o  My rounds were all over the place with each load.  I could not be sure, but looked like I occassionaly either put two rounds into almost the same hole or they were keyholing. :-/
Have cast for handguns for years and had no problems.  This is my first attempt at rifle cast bullets.  Am I using the wrong powder?  Certainly there are better powders for cast, but I shouldn't get results this bad using this powder should I? Totally inappropriate lube?  That is what I used for all my handguns (lower velocity of course, but not really that much higher velocity with the mild Krag load).
I am hoping that one of you experts can tell me what I am doing wrong.  Please help! :'(

Thanks
daveboy