unfortunately, some bullets just don't seem to shoot out of some rifles. I cast a lot of bullets, and some rifles will shoot them, and others will not. All I would suggest if you want to keep shooting your cast bullets... start with about a 60 grain powder charge and start working you load. Also try different sabots as well. Work up in ten grain changes, and see if they will group.

Also try them at closer ranges. For instance I was shooting a Speer Gold Dot and out to 70 yards they shot excellent. At 100 yards, I could not hit a bull in the you know where with that and hold a group...

Just the fact that the rifle started to group with the Shockwaves shows me it was not your shooting skills in question here. So it has to be in load development.