TRES EQUIS,
How big are the groups you are getting? Distance?
You might try positioning the powder to the rear of the case to see if that gives more consistant results by moving the lever to within a 1/4" or so of closing, then raising the muzzle to at least 60 degrees momentarily, then closing the lever the rest of the way after the rifle is in the firing position.
I don't have a Rossi in .45 Colt, but I do have a Marlin Cowboy in that chambering. Mine shoots the 250 gr. bullets better than the 200 gr. As part of what Yellowstone Clay suggested, I would suggest that you try some 250 gr. bullets, but in .454" diameter.
My two favorite loads with this bullet are 8 grs. of 231 or 8.5 grs. of Hogdon's Universal Clays. If I do my part, they are good for 1 1/2" 5 shot groups @ 50 yards.
Good luck,
w30wcf
