I have a rifle that I've worked up a load for and it shoots very well. However I am curious what would happen if I took this barrel off of this rifle and put it on a different action. How much change in the load would occur if I went from a Remington blueprinted action to a Stiller Predator, which is a Rem. clone?

Not saying I'm going to do it for sure, but is this just like starting all over?

I did that exact thing and found myself going back to the drawing board. I guess the barrel harmonics changed as part of the switchout of the action.

I kind of thought that would be the case, but with the chamber and bbl remaining the same, I was thinking that the harmonics would be very close.

Absolutly the truth, "any" change will affect groups.

JMHO, if you swap barrels you change the position of the barrel in the new action, you change the barrel seating surface to surface fit and the torque of the joint.

I don't see how the load performance wouldn't change. It may be to small to make much difference but it also may be a major shift in performance.