I knew there had to be a good use for grits!  (said the northerner! )  Kidding, I actually like the durn things. 
I have used grits over powder in black powder revolvers and as packing in the loose shot in a smoothbore shotgun to prevent the shot from deforming, but never thought to use it in a rifle.  I wonder if a small card wad over the powder and then the grits might help, too.  
MUzzleloading season is three weeks away and I am dialing in the ol' swamped barrel .50 flinter at this time, something else to tinker with!  Thanks!