I have a Guide Gun in .45-70. I shoot cast bullets made by tommy at
www.leadheads.com. I also use IMR 3031. With both the 300gr and the 425gr bullets I shoot clover leafs.
I can't recall off hand how many grains of powder I use under each but if you're interested I can let you know.
I know the amount of powder that I'm shooting is relatively slow.
Just to toot my own horn, four weeks ago, on an 80+ degree day I shot five bullets all touching in a fist shaped bunch. Several guys at the range were wowed.
Tom