Unique is a 45/70 reduced load??

[Johnn Peterson]

If you cast your own gas check bullets and orient the bullet to the bore the same every time those groups will get smaller and more consistent.
A cast bullet needs a really good and true base to be accurate.
And for some reason I have found that when I use an index mark from the mold and load the bullet with the index mark in the same position in the chamber each time the groups drop in size.

True enough. Every measure you take for consistency and to minimize the variation on any of the components and/or procedure, will show up in improved accuracy.