Nice rifle and nice shooting, especially with the original sights.  Looks like you've found a promising bullet/powder combination.  I use IMR 4350 but I've never tried bullets heavier than 180 gr in my Krag sporters.  I'll put 220 gr Sierras on my next Midway shopping list.

Almost forgot to ask, did the last 4 shots alternate between the two locations as you shot or was it two in one hole then two in the other?  It could be a sign of something being loose somewhere.  I had a loose barrel band that would cause groups like that.