Madison, you might want to try some slower burning powders such as Reloder-7 or 2015. I shoot my Ruger #1 a lot, and it invariably wants to group 400-grain class cast bullets into less than 1-inch at 100-yds. Of course the gun is scoped, and fired from a proper benchrest position, but those guns are tack drivers! Good shooting!
Best regards, Randy Garrett
www.garrettcartridges.com