30gr of RL15 under a 220 is going to give you around 1700fps and only 21000psi.  The RL15 may not be burning efficiently at that low pressure, I don't know.  40gr 4350 under a 180 will yield around 2150fps at 34000psi.  Factory fodder will be going around 2400fps with the same 180.  You're going to need a taller front blade.  I don't think you'll be able to get the bullets slow enough to make up the big difference you have.

The start loads of 2520 Accurate shows in their manual for.303 British should be ok for your Krag.  Guess you'd be on your own figuring a start load for 220gr bullets though.