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.   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

That seems like a pretty stiff powder charge for a cast bullet. I use 20 gr of SR4759 with the 195 gr Saeco #301 gas check bullet. My Krag may slug at .309, but the chamber throat is worn and is .315 across in one direction. I seat my gas checks and apply lube using a .314 sizing die. I believe the bullets drop from the mold at about .312

I think I'm using 42 gr of 4895 for a mild load in the M1 Garand, basically just enough to function the rifle. Your 35 gr isn't that far off what I'm using in the 06.

I believe 3031 will load down well. You can't go wrong with a light charge of Unique.

I don't have a lot of cast bullet experience in rifles, but I would start with loads less than 1600 fps.

One other thing - do not load below the min charge weight with a "slow" burning powder (anything slower than say 3031). Use faster powders for low charges. You can blow a gun up with a small charge of slow burning powder (look up secondary explosion effect).

Unique can be a good cast bullet powder for velocities in the very low range. I've never used it as I'm more interested in 200-300 yard loads. The Lyman Cast Bullet Handbook and/or the Lyman #48 should have some cast bullet loads for Unique.