Making cast bullets work well is a science and an art.  Two things will make it easier.  (1)  Slug your bore and cast your bullets .001" larger than the bore.  (2)  Use the right powder and charge--what works for a 140 grain jacketed bullet will usually not work well at all with a cast bullet.  Many other things are involved, but without these two being right you are wasting your time.

Personally, I use a 200 grain gas check slug dropped from a Lee mold.  It consists of wheelweights dropped into water.  I size my bullets to .311" and lube with Lee Liquid Alox.  I load them ahead of 16 grains of Aliant 2400.  This load works very well for me, but each rifle is different.

daveboy