fusion
Gotta have a tight sabot....
Since the MMP Orange is to loose - maybe the combination of the HPH-12 with the Barnes Original .458 willgive you that tightness.
The other options, off the top of my head, is the Barnes in a MMP-Short Black - that should tighten things up and also Harvester is making a 'red crush rib' that also might work.
Here is break down of sabot sizes - that might help...
We do have a Savage shooter on this forum and he always has good information....